A clinical trial for a psychological therapy for trauma takes 37 women and gives them one treatment for trauma and then, a year later, gives them a different treatment. The measure used to indicate success is a Likert scale where 5 means 'l found the treatment very helpful' and 1 means 'l didn't find it helpful at all. The lead researcher gathers the data and she finds a very high variance of scores across the women in each treatment, and considers giving up the analysis. She plans to do a difference in means analysis with unequal variances (she tested and found the variances were unequal). She asks for your advice: a. She is being too hasty because she is using the wrong technique. This is a paired sample and when she takes the difference in the Likert scale for each subject across the two treatments the variance of the remaining lifferences might be so low that she can detect which treatment is statistically better b. She cannot give different treatments to the same people - it violates the rules of random sampling c. None of the other answers are correct d. If the variances across the women are too high any difference in the average Likert scale across the treatments will tend to be insignificant. She is right to be concerned
Inverse Normal Distribution
The method used for finding the corresponding z-critical value in a normal distribution using the known probability is said to be an inverse normal distribution. The inverse normal distribution is a continuous probability distribution with a family of two parameters.
Mean, Median, Mode
It is a descriptive summary of a data set. It can be defined by using some of the measures. The central tendencies do not provide information regarding individual data from the dataset. However, they give a summary of the data set. The central tendency or measure of central tendency is a central or typical value for a probability distribution.
Z-Scores
A z-score is a unit of measurement used in statistics to describe the position of a raw score in terms of its distance from the mean, measured with reference to standard deviation from the mean. Z-scores are useful in statistics because they allow comparison between two scores that belong to different normal distributions.
A clinical trial for a psychological therapy for trauma takes 37 women and gives them one treatment for trauma and then, a year later, gives them a different treatment. The measure used to indicate success is a Likert scale where 5 means 'l found the treatment very helpful' and 1 means 'l didn't find it helpful at all. The lead researcher gathers the data and she finds a very high variance of scores across the women in each treatment, and considers giving up the analysis. She plans to do a difference in means analysis with unequal variances (she tested and found the variances were unequal). She asks for your advice:
a. She is being too hasty because she is using the wrong technique. This is a paired sample and when she takes the difference in the Likert scale for each subject across the two treatments the variance of the remaining lifferences might be so low that she can detect which treatment is statistically better
b. She cannot give different treatments to the same people - it violates the rules of random sampling
c. None of the other answers are correct
d. If the variances across the women are too high any difference in the average Likert scale across the treatments will tend to be insignificant. She is right to be concerned
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