Biostatistics Exercise 1

Biostatistics Exercise 1


The following data give systolic blood pressure measurements in mmHg taken immediately before and 2 hours after the drug captopril.

Patient 1 2 3 4 5 6 7 8 9 10 11 12 13 14 15
Before 210 169 187 160 167 176 185 206 173 146 174 201 198 148 154
After 201 165 160 157 147 145 168 180 147 136 151 168 179 129 131


statistics problems with solutions and answers

Enter the data as 3 columns into jamovi, either directly or via Excel, and label.

  1. Convert the measurement data to Continuous measurement type.
  2. Obtain a descriptive summary for each of the 2 variables: Before and After. Give n, mean, SD, minimum, maximum.
  3. Do not use the Patient variable in any of the analyses. Why do we need it?
  4. Obtain histograms and box plots for each of the 2 variables.
  5. Select Correlation Matrix from the Regression menu in the Analyses Obtain a correlation and p value for Before and After variables. Add a sentence summarizing the analysis, including the kind of relationship between Before and After.
  6. Explain why the relationship seen is not surprising.
  7. From the Exploration menu do a scatterplot, putting Before on the X-axis and After on the Y-axis.
  8. Carry out a regression of After against Before.
  9. Select Model Coefficients and 95% Confidence interval Estimate.
  10. Select Assumption Checks and do Residual plots and Q-Q plot of residuals.
  11. Summarise fully the results of the regression analysis, including comments on the assumption checks.
  12. With a calculator or Excel, use the regression coefficients to obtain the predicted systolic blood pressure after the drug for a patient who had a blood pressure of 180 mmHg before the drug.
  13. Use jamovi to carry out a t test to examine the difference between Before and After. Summarize the results of your analysis and include a plot showing the difference between the two times.