While performing an experiment, a positive control group is given a treatment that was used one time previously in another experiment. This time, however, the positive control does not give the expected result that you received last time. Which of the following is a likely case?
- The equipment or technique to measure the dependent variable is not working properly this time.
-The previous result you obtained was incorrect or flawed.
-A positive control is not useful for this experiment.
Am I right to assume that the answer is the first two choices?
Yes, you are correct in assuming that the first two choices are likely cases for why the positive control group did not give the expected result. Let's break down each option:
1. The equipment or technique to measure the dependent variable is not working properly this time:
In any experiment, it is crucial to ensure that the equipment used to measure the dependent variable is functioning correctly. If the equipment or technique is not working properly, it may lead to inaccurate results or a lack of expected outcomes.
2. The previous result you obtained was incorrect or flawed:
Another possibility is that the previous result obtained from the positive control group was flawed or incorrect. It could be the result of errors in the experiment design, data collection, or data analysis. It's essential to review and validate the previous result to rule out any potential mistakes.
Regarding the third option, "A positive control is not useful for this experiment," this statement is unlikely to be the reason for the unexpected result. A positive control group serves as a baseline to compare against the experimental group, helping to determine if the effect observed in the experimental group is due to the treatment or some other factor. While it is possible that a positive control may not be relevant or appropriate for some experiments, it seems less likely compared to the first two possibilities in this case.
Therefore, your assumption is correct, and the likely cases for the unexpected result are the first two choices.