Saul McLeod published 2012
The prime method of inquiry in science is the experiment. The key features are control over variables, careful measurement, and establishing cause and effect relationships.
An experiment is an investigation in which a hypothesis is scientifically tested. In an experiment, an independent variable (the cause) is manipulated and the dependent variable (the effect) is measured; any extraneous variables are controlled.
An advantage is that experiments should be objective. The views and opinions of the researcher should not affect the results of a study. This is good as it makes the data more valid, and less bias.
There are three types of experiments you need to know:
1. Laboratory / Controlled Experiments
This type of experiment is conducted in a well-controlled environment – not necessarily a laboratory – and therefore accurate measurements are possible.
The researcher decides where the experiment will take place, at what time, with which participants, in what circumstances and using a standardized procedure. Participants are randomly allocated to each independent variable group.
An example is Milgram’s experiment on obedience or Loftus and Palmer's car crash study.
- Strength: It is easier to replicate (i.e. copy) a laboratory experiment. This is because a standardized procedure is used.
- Strength: They allow for precise control of extraneous and independent variables. This allows a cause and effect relationship to be established.
- Limitation: The artificiality of the setting may produce unnatural behavior that does not reflect real life, i.e. low ecological validity. This means it would not be possible to generalize the findings to a real life setting.
- Limitation: Demand characteristics or experimenter effects may bias the results and become confounding variables.
2. Field Experiments
Field experiments are done in the everyday (i.e. real life) environment of the participants. The experimenter still manipulates the independent variable, but in a real-life setting (so cannot really control extraneous variables).
An example is Holfing’s hospital study on obedience.
- Strength: Behavior in a field experiment is more likely to reflect real life because of its natural setting, i.e. higher ecological validity than a lab experiment.
- Strength: There is less likelihood of demand characteristics affecting the results, as participants may not know they are being studied. This occurs when the study is covert.
- Limitation: There is less control over extraneous variables that might bias the results. This makes it difficult for another researcher to replicate the study in exactly the same way.
3. Natural Experiments
Natural experiments are conducted in the everyday (i.e. real life) environment of the participants, but here the experimenter has no control over the IV as it occurs naturally in real life.
For example, Hodges and Tizard's attachment research (1989) compared the long term development of children who have been adopted, fostered or returned to their mothers with a control group of children who had spent all their lives in their biological families.
- Strength: Behavior in a natural experiment is more likely to reflect real life because of its natural setting, i.e. very high ecological validity.
- Strength: There is less likelihood of demand characteristics affecting the results, as participants may not know they are being studied.
- Strength: Can be used in situations in which it would be ethically unacceptable to manipulate the independent variable, e.g. researching stress.
- Limitation: They may be more expensive and time consuming than lab experiments.
- Limitation: There is no control over extraneous variables that might bias the results. This makes it difficult for another researcher to replicate the study in exactly the same way.
The degree to which an investigation represents real-life experiences.
These are the ways that the experimenter can accidentally influence the participant through their appearance or behavior.
The clues in an experiment that lead the participants to think they know what the researcher is looking for (e.g. experimenter’s body language).
Independent variable (IV)
Variable the experimenter manipulates (i.e. changes) – assumed to have a direct effect on the dependent variable.
Dependent variable (DV)
Variable the experimenter measures. This is the outcome (i.e. result) of a study.
Extraneous variables (EV)
All variables, which are not the independent variable, but could affect the results (DV) of the experiment. EVs should be controlled where possible.
Variable(s) that have affected the results (DV), apart from the IV. A confounding variable could be an extraneous variable that has not been controlled.
Randomly allocating participants to independent variable conditions means that all participants should have an equal chance of taking part in each condition.
The principle of random allocation is to avoid bias in the way the experiment is carried out and to limit the effects of participant variables.
Changes in participants’ performance due to their repeating the same or similar test more than once. Examples of order effects include:
(i) practice effect: an improvement in performance on a task due to repetition, for example, because of familiarity with the task;
(ii) fatigue effect: a decrease in performance of a task due to repetition, for example, because of boredom or tiredness.
How to reference this article:
McLeod, S. A. (2012). Experimental method. Retrieved from www.simplypsychology.org/experimental-method.html
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This paper should be used only as an example of a research paper write-up. Horizontal rules signify the top and bottom edges of pages. For sample references which are not included with this paper, you should consult the Publication Manual of the American Psychological Association, 4th Edition.
This paper is provided only to give you an idea of what a research paper might look like. You are not allowed to copy any of the text of this paper in writing your own report.
Because word processor copies of papers don't translate well into web pages, you should note that an actual paper should be formatted according to the formatting rules for your context. Note especially that there are three formatting rules you will see in this sample paper which you should NOT follow. First, except for the title page, the running header should appear in the upper right corner of every page with the page number below it. Second, paragraphs and text should be double spaced and the start of each paragraph should be indented. Third, horizontal lines are used to indicate a mandatory page break and should not be used in your paper.
The Effects of a Supported Employment Program on Psychosocial Indicators
for Persons with Severe Mental Illness
William M.K. Trochim
Running Head: SUPPORTED EMPLOYMENT
This paper describes the psychosocial effects of a program of supported employment (SE) for persons with severe mental illness. The SE program involves extended individualized supported employment for clients through a Mobile Job Support Worker (MJSW) who maintains contact with the client after job placement and supports the client in a variety of ways. A 50% simple random sample was taken of all persons who entered the Thresholds Agency between 3/1/93 and 2/28/95 and who met study criteria. The resulting 484 cases were randomly assigned to either the SE condition (treatment group) or the usual protocol (control group) which consisted of life skills training and employment in an in-house sheltered workshop setting. All participants were measured at intake and at 3 months after beginning employment, on two measures of psychological functioning (the BPRS and GAS) and two measures of self esteem (RSE and ESE). Significant treatment effects were found on all four measures, but they were in the opposite direction from what was hypothesized. Instead of functioning better and having more self esteem, persons in SE had lower functioning levels and lower self esteem. The most likely explanation is that people who work in low-paying service jobs in real world settings generally do not like them and experience significant job stress, whether they have severe mental illness or not. The implications for theory in psychosocial rehabilitation are considered.
The Effects of a Supported Employment Program on Psychosocial Indicators for Persons with Severe Mental Illness
Over the past quarter century a shift has occurred from traditional institution-based models of care for persons with severe mental illness (SMI) to more individualized community-based treatments. Along with this, there has been a significant shift in thought about the potential for persons with SMI to be "rehabilitated" toward lifestyles that more closely approximate those of persons without such illness. A central issue is the ability of a person to hold a regular full-time job for a sustained period of time. There have been several attempts to develop novel and radical models for program interventions designed to assist persons with SMI to sustain full-time employment while living in the community. The most promising of these have emerged from the tradition of psychiatric rehabilitation with its emphases on individual consumer goal setting, skills training, job preparation and employment support (Cook, Jonikas and Solomon, 1992). These are relatively new and field evaluations are rare or have only recently been initiated (Cook and Razzano, 1992; Cook, 1992). Most of the early attempts to evaluate such programs have naturally focused almost exclusively on employment outcomes. However, theory suggests that sustained employment and living in the community may have important therapeutic benefits in addition to the obvious economic ones. To date, there have been no formal studies of the effects of psychiatric rehabilitation programs on key illness-related outcomes. To address this issue, this study seeks to examine the effects of a new program of supported employment on psychosocial outcomes for persons with SMI.
Over the past several decades, the theory of vocational rehabilitation has experienced two major stages of evolution. Original models of vocational rehabilitation were based on the idea of sheltered workshop employment. Clients were paid a piece rate and worked only with other individuals who were disabled. Sheltered workshops tended to be "end points" for persons with severe and profound mental retardation since few ever moved from sheltered to competitive employment (Woest, Klein & Atkins, 1986). Controlled studies of sheltered workshop performance of persons with mental illness suggested only minimal success (Griffiths, 1974) and other research indicated that persons with mental illness earned lower wages, presented more behavior problems, and showed poorer workshop attendance than workers with other disabilities (Whitehead, 1977; Ciardiello, 1981).
In the 1980s, a new model of services called Supported Employment (SE) was proposed as less expensive and more normalizing for persons undergoing rehabilitation (Wehman, 1985). The SE model emphasizes first locating a job in an integrated setting for minimum wage or above, and then placing the person on the job and providing the training and support services needed to remain employed (Wehman, 1985). Services such as individualized job development, one-on-one job coaching, advocacy with co-workers and employers, and "fading" support were found to be effective in maintaining employment for individuals with severe and profound mental retardation (Revell, Wehman & Arnold, 1984). The idea that this model could be generalized to persons with all types of severe disabilities, including severe mental illness, became commonly accepted (Chadsey-Rusch & Rusch, 1986).
One of the more notable SE programs was developed at Thresholds, the site for the present study, which created a new staff position called the mobile job support worker (MJSW) and removed the common six month time limit for many placements. MJSWs provide ongoing, mobile support and intervention at or near the work site, even for jobs with high degrees of independence (Cook & Hoffschmidt, 1993). Time limits for many placements were removed so that clients could stay on as permanent employees if they and their employers wished. The suspension of time limits on job placements, along with MJSW support, became the basis of SE services delivered at Thresholds.
There are two key psychosocial outcome constructs of interest in this study. The first is the overall psychological functioning of the person with SMI. This would include the specification of severity of cognitive and affective symptomotology as well as the overall level of psychological functioning. The second is the level of self-reported self esteem of the person. This was measured both generally and with specific reference to employment.
The key hypothesis of this study is:
HO: A program of supported employment will result in either no change or negative effects on psychological functioning and self esteem.
which will be tested against the alternative:
HA: A program of supported employment will lead to positive effects on psychological functioning and self esteem.
The population of interest for this study is all adults with SMI residing in the U.S. in the early 1990s. The population that is accessible to this study consists of all persons who were clients of the Thresholds Agency in Chicago, Illinois between the dates of March 1, 1993 and February 28, 1995 who met the following criteria: 1) a history of severe mental illness (e.g., either schizophrenia, severe depression or manic-depression); 2) a willingness to achieve paid employment; 3) their primary diagnosis must not include chronic alcoholism or hard drug use; and 4) they must be 18 years of age or older. The sampling frame was obtained from records of the agency. Because of the large number of clients who pass through the agency each year (e.g., approximately 500 who meet the criteria) a simple random sample of 50% was chosen for inclusion in the study. This resulted in a sample size of 484 persons over the two-year course of the study.
On average, study participants were 30 years old and high school graduates (average education level = 13 years). The majority of participants (70%) were male. Most had never married (85%), few (2%) were currently married, and the remainder had been formerly married (13%). Just over half (51%) are African American, with the remainder Caucasian (43%) or other minority groups (6%). In terms of illness history, the members in the sample averaged 4 prior psychiatric hospitalizations and spent a lifetime average of 9 months as patients in psychiatric hospitals. The primary diagnoses were schizophrenia (42%) and severe chronic depression (37%). Participants had spent an average of almost two and one-half years (29 months) at the longest job they ever held.
While the study sample cannot be considered representative of the original population of interest, generalizability was not a primary goal -- the major purpose of this study was to determine whether a specific SE program could work in an accessible context. Any effects of SE evident in this study can be generalized to urban psychiatric agencies that are similar to Thresholds, have a similar clientele, and implement a similar program.
All but one of the measures used in this study are well-known instruments in the research literature on psychosocial functioning. All of the instruments were administered as part of a structured interview that an evaluation social worker had with study participants at regular intervals.
Two measures of psychological functioning were used. The Brief Psychiatric Rating Scale (BPRS)(Overall and Gorham, 1962) is an 18-item scale that measures perceived severity of symptoms ranging from "somatic concern" and "anxiety" to "depressive mood" and "disorientation." Ratings are given on a 0-to-6 Likert-type response scale where 0="not present" and 6="extremely severe" and the scale score is simply the sum of the 18 items. The Global Assessment Scale (GAS)(Endicott et al, 1976) is a single 1-to-100 rating on a scale where each ten-point increment has a detailed description of functioning (higher scores indicate better functioning). For instance, one would give a rating between 91-100 if the person showed "no symptoms, superior functioning..." and a value between 1-10 if the person "needs constant supervision..."
Two measures of self esteem were used. The first is the Rosenberg Self Esteem (RSE) Scale (Rosenberg, 1965), a 10-item scale rated on a 6-point response format where 1="strongly disagree" and 6="strongly agree" and there is no neutral point. The total score is simply the sum across the ten items, with five of the items being reversals. The second measure was developed explicitly for this study and was designed to measure the Employment Self Esteem (ESE) of a person with SMI. This is a 10-item scale that uses a 4-point response format where 1="strongly disagree" and 4="strongly agree" and there is no neutral point. The final ten items were selected from a pool of 97 original candidate items, based upon high item-total score correlations and a judgment of face validity by a panel of three psychologists. This instrument was deliberately kept simple -- a shorter response scale and no reversal items -- because of the difficulties associated with measuring a population with SMI. The entire instrument is provided in Appendix A.
All four of the measures evidenced strong reliability and validity. Internal consistency reliability estimates using Cronbach's alpha ranged from .76 for ESE to .88 for SE. Test-retest reliabilities were nearly as high, ranging from .72 for ESE to .83 for the BPRS. Convergent validity was evidenced by the correlations within construct. For the two psychological functioning scales the correlation was .68 while for the self esteem measures it was somewhat lower at .57. Discriminant validity was examined by looking at the cross-construct correlations which ranged from .18 (BPRS-ESE) to .41 (GAS-SE).
A pretest-posttest two-group randomized experimental design was used in this study. In notational form, the design can be depicted as:
R O X O
R O O
R = the groups were randomly assigned
O = the four measures (i.e., BPRS, GAS, RSE, and ESE)
X = supported employment
The comparison group received the standard Thresholds protocol which emphasized in-house training in life skills and employment in an in-house sheltered workshop. All participants were measured at intake (pretest) and at three months after intake (posttest).
This type of randomized experimental design is generally strong in internal validity. It rules out threats of history, maturation, testing, instrumentation, mortality and selection interactions. Its primary weaknesses are in the potential for treatment-related mortality (i.e., a type of selection-mortality) and for problems that result from the reactions of participants and administrators to knowledge of the varying experimental conditions. In this study, the drop-out rate was 4% (N=9) for the control group and 5% (N=13) in the treatment group. Because these rates are low and are approximately equal in each group, it is not plausible that there is differential mortality. There is a possibility that there were some deleterious effects due to participant knowledge of the other group's existence (e.g., compensatory rivalry, resentful demoralization). Staff were debriefed at several points throughout the study and were explicitly asked about such issues. There were no reports of any apparent negative feelings from the participants in this regard. Nor is it plausible that staff might have equalized conditions between the two groups. Staff were given extensive training and were monitored throughout the course of the study. Overall, this study can be considered strong with respect to internal validity.
Between 3/1/93 and 2/28/95 each person admitted to Thresholds who met the study inclusion criteria was immediately assigned a random number that gave them a 50/50 chance of being selected into the study sample. For those selected, the purpose of the study was explained, including the nature of the two treatments, and the need for and use of random assignment. Participants were assured confidentiality and were given an opportunity to decline to participate in the study. Only 7 people (out of 491) refused to participate. At intake, each selected sample member was assigned a random number giving them a 50/50 chance of being assigned to either the Supported Employment condition or the standard in-agency sheltered workshop. In addition, all study participants were given the four measures at intake.
All participants spent the initial two weeks in the program in training and orientation. This consisted of life skill training (e.g., handling money, getting around, cooking and nutrition) and job preparation (employee roles, coping strategies). At the end of that period, each participant was assigned to a job site -- at the agency sheltered workshop for those in the control condition, and to an outside employer if in the Supported Employment group. Control participants were expected to work full-time at the sheltered workshop for a three-month period, at which point they were posttested and given an opportunity to obtain outside employment (either Supported Employment or not). The Supported Employment participants were each assigned a case worker -- called a Mobile Job Support Worker (MJSW) -- who met with the person at the job site two times per week for an hour each time. The MJSW could provide any support or assistance deemed necessary to help the person cope with job stress, including counseling or working beside the person for short periods of time. In addition, the MJSW was always accessible by cellular telephone, and could be called by the participant or the employer at any time. At the end of three months, each participant was post-tested and given the option of staying with their current job (with or without Supported Employment) or moving to the sheltered workshop.
There were 484 participants in the final sample for this study, 242 in each treatment. There were 9 drop-outs from the control group and 13 from the treatment group, leaving a total of 233 and 229 in each group respectively from whom both pretest and posttest were obtained. Due to unexpected difficulties in coping with job stress, 19 Supported Employment participants had to be transferred into the sheltered workshop prior to the posttest. In all 19 cases, no one was transferred prior to week 6 of employment, and 15 were transferred after week 8. In all analyses, these cases were included with the Supported Employment group (intent-to-treat analysis) yielding treatment effect estimates that are likely to be conservative.
The major results for the four outcome measures are shown in Figure 1.
Insert Figure 1 about here
It is immediately apparent that in all four cases the null hypothesis has to be accepted -- contrary to expectations, Supported Employment cases did significantly worse on all four outcomes than did control participants.
The mean gains, standard deviations, sample sizes and t-values (t-test for differences in average gain) are shown for the four outcome measures in Table 1.
Insert Table 1 about here
The results in the table confirm the impressions in the figures. Note that all t-values are negative except for the BPRS where high scores indicate greater severity of illness. For all four outcomes, the t-values were statistically significant (p<.05).
The results of this study were clearly contrary to initial expectations. The alternative hypothesis suggested that SE participants would show improved psychological functioning and self esteem after three months of employment. Exactly the reverse happened -- SE participants showed significantly worse psychological functioning and self esteem.
There are two major possible explanations for this outcome pattern. First, it seems reasonable that there might be a delayed positive or "boomerang" effect of employment outside of a sheltered setting. SE cases may have to go through an initial difficult period of adjustment (longer than three months) before positive effects become apparent. This "you have to get worse before you get better" theory is commonly held in other treatment-contexts like drug addiction and alcoholism. But a second explanation seems more plausible -- that people working full-time jobs in real-world settings are almost certainly going to be under greater stress and experience more negative outcomes than those who work in the relatively safe confines of an in-agency sheltered workshop. Put more succinctly, the lesson here might very well be that work is hard. Sheltered workshops are generally very nurturing work environments where virtually all employees share similar illness histories and where expectations about productivity are relatively low. In contrast, getting a job at a local hamburger shop or as a shipping clerk puts the person in contact with co-workers who may not be sympathetic to their histories or forgiving with respect to low productivity. This second explanation seems even more plausible in the wake of informal debriefing sessions held as focus groups with the staff and selected research participants. It was clear in the discussion that SE persons experienced significantly higher job stress levels and more negative consequences. However, most of them also felt that the experience was a good one overall and that even their "normal" co-workers "hated their jobs" most of the time.
One lesson we might take from this study is that much of our contemporary theory in psychiatric rehabilitation is naive at best and, in some cases, may be seriously misleading. Theory led us to believe that outside work was a "good" thing that would naturally lead to "good" outcomes like increased psychological functioning and self esteem. But for most people (SMI or not) work is at best tolerable, especially for the types of low-paying service jobs available to study participants. While people with SMI may not function as well or have high self esteem, we should balance this with the desire they may have to "be like other people" including struggling with the vagaries of life and work that others struggle with.
Future research in this are needs to address the theoretical assumptions about employment outcomes for persons with SMI. It is especially important that attempts to replicate this study also try to measure how SE participants feel about the decision to work, even if traditional outcome indicators suffer. It may very well be that negative outcomes on traditional indicators can be associated with a "positive" impact for the participants and for the society as a whole.
Chadsey-Rusch, J. and Rusch, F.R. (1986). The ecology of the workplace. In J. Chadsey-Rusch, C. Haney-Maxwell, L. A. Phelps and F. R. Rusch (Eds.), School-to-Work Transition Issues and Models. (pp. 59-94), Champaign IL: Transition Institute at Illinois.
Ciardiello, J.A. (1981). Job placement success of schizophrenic clients in sheltered workshop programs. Vocational Evaluation and Work Adjustment Bulletin, 14, 125-128, 140.
Cook, J.A. (1992). Job ending among youth and adults with severe mental illness. Journal of Mental Health Administration, 19(2), 158-169.
Cook, J.A. & Hoffschmidt, S. (1993). Psychosocial rehabilitation programming: A comprehensive model for the 1990's. In R.W. Flexer and P. Solomon (Eds.), Social and Community Support for People with Severe Mental Disabilities: Service Integration in Rehabilitation and Mental Health. Andover, MA: Andover Publishing.
Cook, J.A., Jonikas, J., & Solomon, M. (1992). Models of vocational rehabilitation for youth and adults with severe mental illness. American Rehabilitation, 18, 3, 6-32.
Cook, J.A. & Razzano, L. (1992). Natural vocational supports for persons with severe mental illness: Thresholds Supported Competitive Employment Program, in L. Stein (ed.), New Directions for Mental Health Services, San Francisco: Jossey-Bass, 56, 23-41.
Endicott, J.R., Spitzer, J.L. Fleiss, J.L. and Cohen, J. (1976). The Global Assessment Scale: A procedure for measuring overall severity of psychiatric disturbance. Archives of General Psychiatry, 33, 766-771.
Griffiths, R.D. (1974). Rehabilitation of chronic psychotic patients. Psychological Medicine, 4, 316-325.
Overall, J. E. and Gorham, D. R. (1962). The Brief Psychiatric Rating Scale. Psychological Reports, 10, 799-812.
Rosenberg, M. (1965). Society and Adolescent Self Image. Princeton, NJ, Princeton University Press.
Wehman, P. (1985). Supported competitive employment for persons with severe disabilities. In P. McCarthy, J. Everson, S. Monn & M. Barcus (Eds.), School-to-Work Transition for Youth with Severe Disabilities, (pp. 167-182), Richmond VA: Virginia Commonwealth University.
Whitehead, C.W. (1977). Sheltered Workshop Study: A Nationwide Report on Sheltered Workshops and their Employment of Handicapped Individuals. (Workshop Survey, Volume 1), U.S. Department of Labor Service Publication. Washington, DC: U.S. Government Printing Office.
Woest, J., Klein, M. and Atkins, B.J. (1986). An overview of supported employment strategies. Journal of Rehabilitation Administration, 10(4), 130-135.
Table 1. Means, standard deviations and Ns for the pretest, posttest and gain scores for the four outcome variables and t-test for difference between average gains.
Figure 1. Pretest and posttest means for treatment (SE) and control groups for the four outcome measures.
The Employment Self Esteem Scale
Please rate how strongly you agree or disagree with each of the following statements.
|1. I feel good about my work on the job.|
|2. On the whole, I get along well with others at work.|
|3. I am proud of my ability to cope with difficulties at work.|
|4. When I feel uncomfortable at work, I know how to handle it.|
|5. I can tell that other people at work are glad to have me there.|
|6. I know I'll be able to cope with work for as long as I want.|
|7. I am proud of my relationship with my supervisor at work.|
|8. I am confident that I can handle my job without constant assistance.|
|9. I feel like I make a useful contribution at work.|
|10. I can tell that my co-workers respect me.|
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