You have been called upon to assess whether a NICU nutrition protocol is working to promote growth in underweight babies. You have weight measurements at three time points: birth, 28 days and discharge from the hospital. You also have a variable indicating whether the babies met all their nutritional goals in addition to a few other variables. Carry out a within and between analysis on the appropriate variables. Rather than carry out the analysis all at once, we are going to enter terms into the model in a step-by-step fashion. The idea is to help you see how what we are doing this week is largely just a matter of putting together the pieces we've learned up till now. Use the SPSS Repeated Measures GLM output to answer the following questions. You first want to determine if, for all NICU patients, there is a significant change in weight.
Specifically, you are interested in determining if there is a change in weight: across the entire period (all measurements) from birth to 28 days and from 28 days to discharge. 1. What null hypotheses would you test (hint: there are three separate hypotheses you are testing)?
2. So, before you carry out your analysis, think about what kinds of comparisons you want to make. If we want to focus on how babies' weight changes in two distinct periods (birth to 28 days and then 28 days to discharge), what type of contrast would we want to choose? Select one: a. Deviation b. Simple c. Difference d. Helmert e. Repeated f. Polynomial
3. What is the significance of the Mauchly's test of sphericity?
What is a reasonable approach when the Mauchly's significance is at the level you find in this example? Sphericity is tenable, so use the standard F test results to interpret the findings Since sphericity is not tenable, we cannot use the GLM repeated measures procedure to answer our question Since sphericity is not tenable, we should use one of the modified F statistics to interpret the findings 4. What is the value of the test statistic and significance for the following tests (report the result of the most conservative F test):
1. The overall trajectory of weight change for the babies across the entire time period: F statistic Answer p value Answer
2. The difference between weight at birth and 28 days: F statistic Answer p value Answer
3. The difference between weight at 28 days and dischange: F statistic Answer p value Answer
5. Interpret the findings (use a plot to help interpret if appropriate) in an MS Word file. If there is a significant change in weight during a particular period, be sure and give your reader a sense of how much (and direction) change there was.