t-tests and graphing using Excel
Round all calculated values to 2 decimal places.
Download this file for the homework assignment: Calcium_BP.xls. To download this file in Internet Explorer, right-click on the link, left-click on Save Target As ...., left-click on Save, the file will download. When the download is completed, left-click on Close.
Open the file Calcium_BP.xls in Microsoft Excel. To do this, start Excel, left-click on File > Open, locate and single left-click the file in the Open dialog box, and left-click Open.
The data set for this problem reports the results of a randomized comparative experiment to investigate the effect of calcium on systolic blood pressure in African-American men. A treatment group of 10 men received a calcium supplement for 12 weeks, and a control group of 11 men received a placebo during the same period. All subjects had their blood pressure tested before and after the 12-week period.
The citation for this work is: Moore, David S., and George P. McCabe (1989). Introduction to the Practice of Statistics. Original source: Lyle, Roseann M., et al., "Blood pressure and metabolic effects of calcium supplementation in normotensive white and black men," JAMA, 257(1987), pp. 1772-1776.
For Questions (1) - (3), perform the following steps to answer the question posed:
Make sure to label your work for each question clearly in the Excel spreadsheet or on any other pages you submit.
Round all numeric answers to 2 decimal places.
For each problem:
(A) State the null and alternative hypotheses. Make sure to pay attention to directionality (or lack of).
(B) Compute the appropriate test value and critical value. Label these clearly (highlight them) on your printout.
(C) State your decision about your hypotheses.
(D) Graph you data (bar graph with confidence intervals that you calculate using the TINV function)
(E) State your results. This should relate to the question, not just the hypotheses.
1. Determine if there is a significant difference between the beginning and ending systolic blood pressure values in the calcium versus the placebo group. Use alpha ≤ 0.05 for this comparison.
2. Using only the beginning systolic blood pressure data, was there a difference between the subjects in the calcium versus the placebo group? Use alpha ≤ 0.01 for this comparison.
3. Consider just the calcium group's ending systolic blood pressure. Assume that the population of all individuals has a mean systolic blood pressure of 115. Do the subjects in the calcium group have a lower systolic blood pressure compared to the population? Use alpha ≤ 0.10 for this comparison.