Final answer:
To analyze the effectiveness of CBT for anorexia patients, select patients treated with CBT, construct a box and whisker plot, compute summary statistics, check variance equality, and conduct hypothesis testing at a 5% significance level.
Step-by-step explanation:
This question pertains to the effectiveness of Cognitive Behavioral Therapy (CBT) for anorexia patients based on weight data before and after the treatment present in the MASS R package.
- To select patients treated with CBT only, one would typically subset the data based on the treatment variable using R's subsetting functions.
- For constructing a side-by-side box and whisker plot for Postut (weight after treatment) and Prest (weight before treatment), functions like boxplot() could be applied, and the distributions of each plot can be commented upon by observing their medians, quartiles, range, and potential outliers.
- Summary statistics for Postut and Prowt (presumably a typo and should refer to Prest) could be obtained using the summary() or describe() function in R and would include measures such as mean, median, quartile, and standard deviation.
- To check for equality of variances, a statistical test such as Levene's Test or an F-test could be performed. If the variances are not approximately equal, it may affect the type of statistical test used to compare the means.
- Finally, to address the Psychologist's assertion regarding the effectiveness of CBT, a paired t-test or a nonparametric equivalent could be used to compare the means of Postut and Prest at a 5% significance level and draw conclusions based upon the p-value and confidence intervals obtained.
Based on these analyses, one can then make an informed decision on whether the data supports the claim of the effectiveness of CBT for anorexia patients.