One-Shot Case Study
X
X --> O--> O11
In this design, a treatment is implemented, following which an observation is In this design, a treatment is implemented, following which an observation is conducted.
conducted. The implied assumption is that The implied assumption is that whatever happened in the whatever happened in the treatmenttreatment influenced what was found
influenced what was found in the observation. in the observation. However, since there is nothingHowever, since there is nothing
with which to compare the observation, there is no way to ascertain with with which to compare the observation, there is no way to ascertain with confidence whether the treatment had any influence at all on the findings.
confidence whether the treatment had any influence at all on the findings.
Using our feedback example for this design, we would expect to see the Using our feedback example for this design, we would expect to see the researcher implement a plan of providing feedback to students during math researcher implement a plan of providing feedback to students during math instruction (
instruction ( X X ). ). The researcher would then The researcher would then look at student look at student performance on theperformance on the math test following the instruction (
math test following the instruction ( OO). ). Since the Since the researcher has no researcher has no other data,other data, there is no way to tell whether the test performance was higher or lower than it there is no way to tell whether the test performance was higher or lower than it would have been without the feedback.
would have been without the feedback.
One-Group Pretest-Posttest Design One-Group Pretest-Posttest Design
O
O11 ---->> X X ---->> OO2 2
This design uses a pretreatment observation as an attempt to provide some basis This design uses a pretreatment observation as an attempt to provide some basis for comparison
for comparison for the for the post-treatment observation. post-treatment observation. Presumably, the differencePresumably, the difference between the post-treatment observation and the pretreatment observation is a between the post-treatment observation and the pretreatment observation is a consequence of the intervening treatment, but again the researcher’s confidence consequence of the intervening treatment, but again the researcher’s confidence in the findings must be low.
in the findings must be low. There is no way of There is no way of knowing what the differenceknowing what the difference between the two observations would have been without any intervening between the two observations would have been without any intervening treatment.
treatment.
Applying o
Applying our feedbur feedback exampack example to this dle to this design, we esign, we see that see that the reseathe researcher rcher has measured student math performance (
has measured student math performance ( OO11) prior to the instruction with) prior to the instruction with feedback (
feedback ( X X ) and measures math performance again following the instruction) and measures math performance again following the instruction ((OO22). ). The The comparison comparison of of OO11toto OO22will show whether or not there was a gain (or will show whether or not there was a gain (or loss) in math performance.
loss) in math performance. Since the reason Since the reason for the research was for the research was to investigateto investigate the effect of providing feedback, and since there is no way of being sure that the the effect of providing feedback, and since there is no way of being sure that the difference between
difference between OO22andand OO11was due to feedback, the instruction, or somethingwas due to feedback, the instruction, or something else, the researcher still cannot answer the question about the usefulness of else, the researcher still cannot answer the question about the usefulness of feedback.
feedback.
Intact-Group Comparison Intact-Group Comparison
X
X --> O--> O11
O O22
Here the researcher used a comparison group that received no treatment (often Here the researcher used a comparison group that received no treatment (often referred to as a
referred to as a control groupcontrol group). ). Now there Now there is some is some element of element of control throughcontrol through the use of a comparison between the two groups, one of which received the the use of a comparison between the two groups, one of which received the treatment and the other of
treatment and the other of which did not. which did not. This comparison is only useful if the twoThis comparison is only useful if the two groups were equivalent to begin with, but in this design, unfortunately, there is no groups were equivalent to begin with, but in this design, unfortunately, there is no basis for thinking that they were.
basis for thinking that they were.
In this situation the researcher gave the students in the first group In this situation the researcher gave the students in the first group instruction with feedback (
instruction with feedback ( X X ) and the students in the second group instruction) and the students in the second group instruction with no feedback.
with no feedback. Following the instruction, the math scores Following the instruction, the math scores from both groupsfrom both groups ((OO11andand OO22) were compared. ) were compared. As was mentioned As was mentioned earlier, the comparison of theearlier, the comparison of the math scores of the two groups is useful if we can be confident that the groups math scores of the two groups is useful if we can be confident that the groups were equivalent prior to instruction.
were equivalent prior to instruction.
In all of the designs described in this section, there are serious flaws that In all of the designs described in this section, there are serious flaws that render the results of
render the results of studies using these designs studies using these designs virtually useless. virtually useless. In order toIn order to obtain data that allows meaningful and useful comparisons, a researcher must obtain data that allows meaningful and useful comparisons, a researcher must use more rigorous designs, some of which are described in the following
use more rigorous designs, some of which are described in the following sections.
sections.