Statistical Tests: Chi-square Page 1/3
A study was set up to look at whether there was a difference in the mean arterial blood pressure between two groups of volunteers, after 6 weeks of following one of two treatment programs. One group of volunteers were given an exercise regimen to follow for the 6 weeks and the other group were given the same exercise regimen with the addition of an experimental tablet.
The table below shows the number of patients who developed an infection while in hospital as well as those who remained infection free. The results from two different hospitals over the same time period are displayed.
|
Infection |
No Infection |
Total |
|
|
Hospital A |
16 |
237 |
253 |
|
Hospital B |
27 |
594 |
621 |
A study was set up to look at whether overweight patients were able to meet their target weight loss, after 6 weeks of following one of two treatment programs. One group of patients were given an exercise regimen to follow for the 6 weeks and the other group were given the same exercise regimen with the addition of an experimental tablet.
A study was set up to look at whether overweight patients were able to meet their target weight loss, after 6 weeks of following one of three treatment programs. One group of patients were given an exercise regimen to follow for the 6 weeks, another group was given the same exercise regimen with the addition of an experimental tablet and the third group were given a placebo tablet.
In a study patients had their BMI classified as either normal (18.5 to 25) or not normal. These patients were then all asked to follow a 6 week exercise regimen. Their BMI was then classified again (in the same way) after the intervention had finished.
The table below shows the number of patients who developed an infection while in hospital as well as those who remained infection free. The results from two different hospitals over the same time period are displayed.
|
Infection |
No Infection |
Total |
|
|
Hospital A |
16 |
237 |
253 |
|
Hospital B |
27 |
594 |
621 |
Welcome to the "Chi-square" quiz. There are 7 questions to answer.
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Q1. Should a Chi-square test be used in this situation?
The answer is b). As we are wanting to compare the mean arterial blood pressure between the two groups then a test that is used for continuous outcomes is required. As such a Chi-square test is not appropriate here.
Q2. If we wanted to produce a graphical display to summarise all of this data then which of the following chart types could be used (select all that apply)?
The answer is f). As we want to display infection and non-infection separately for each hospital then we need to use a clustered bar chart. If we only had one hospital that we were interested in, or if we only wanted to display infections or non-infections then a normal bar chart would be suitable.
Q3. Should a Chi-square test be considered in this situation?
The answer is a). As we would be wanting to compare the proportion of individuals meeting their weight loss targets following treatment then a test that is used for categorical outcomes is required. As we are also comparing two independent groups of patients then a Chi-square test should be considered here.
Q4. Should a Chi-square test be considered in this situation?
The answer is a). As we would be wanting to compare the proportion of individuals meeting their weight loss targets following treatment then a test that is used for categorical outcomes is required. As we are also comparing two independent groups of patients then a Chi-square test should be considered here.
Q5. If we are interested in the change in state from baseline to post intervention then should a Chi-square test be considered in this situation?
The answer is b). As we would be looking at BMI classifications which have two levels, then a test that is used for categorical outcomes is required. However because we are looking at paired data (we are looking to see whether an individual classification changes or not) the Chi-square test is not appropriate in this case. McNemars test would be more appropriate here.
Q6. If we wanted to compare the proportion of patients who developed an infection between the two hospitals then which of the following statistical tests should we consider (select all that apply)?
The answers are c) and e).
Q7. If we wanted to compare the proportion of patients who developed an infection between the two hospitals then which of the following statistical tests should we use (select the best answer)?
The answer is c).
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