# Biostatistics Exercise 2

Biostatistics Exercise 2

1. Serum thyroxine levels (nmol/L) were recorded for hypothyroid infants. One group had no symptoms while in the second group symptoms were present.
 None 34 45 49 55 58 59 60 62 86 Present 5 8 18 24 60 84 96

Enter the data into jamovi, label the columns and set the appropriate measure type.

1. Is this an experimental or quasi-experimental design?
2. Carry out a Welch test to determine whether there was a statistical difference between the two groups of patients. Summarise fully the results of this analysis.
3. Include a Descriptives plot from the analysis, showing 95% confidence interval error bars.
4. Comment on the plot.

1. With the same data as in the first question:
2. Carry out a Mann-Whitney U test and summarize fully the results of the analysis.
3. Obtain a boxplot for the two groups of patients to include with your answer.
4. How similar are the results of the Welch and Mann-Whitney tests?

## Carry out a Mann-Whitney U test and summarize fully the results of the analysis

Biostatistics Exercise 2

1. The following data consist of relative fluorescent levels for PLC-zeta in sperm following 3 different types assisted reproductive technologies (A, B and C). Two different age groups for the men were recorded.
 Aged under 50 years Aged 50 years and older A 6.8 12.3 4.9 12.5 9.7 5.7 7.8 9.1 7.2 2.5 8.4 7.6 B 16.5 18.2 14.2 17.6 10.2 16.9 8.7 5.7 10 7.2 5.5 11.2 C 8.2 13.8 7.4 11.2 10 6.9 4.4 8.6 10.2 8.8 4.2 7.4

Enter the data into jamovi in 3 columns, one containing the data, the second containing the letters A, B, C to indicate treatment, and the third coding for age group. Label and set data type appropriately.

1. Carry out a two-way ANOVA to test for main effects and the interaction.
2. Check the assumptions for the analysis. Are all 3 satisfied?
3. Obtain a plot of the marginal means.
4. Summarise fully the results of your analysis.

### Use the Poisson distribution to calculate the probability

Biostatistics Exercise 2

1. The mean number of COVID-19 patients admitted to a particular hospital is 4.2 per day. The hospital would be overwhelmed if more than 8 patients were admitted in a day.
2. Use the Poisson distribution to calculate the probability that the hospital would be overwhelmed on any particular day.
3. Calculate the number of days in the year that the hospital is likely to be overwhelmed.

1. Staff at a hospital were surveyed on their use of analgesic medications, such as paracetamol. They were asked whether they had used analgesic medications in the last week. The data were:
Physicians Pharmacists Nurses
 Use analgesic medications
Used 19 28 85
Not used 43 26 51

1. Enter the data into jamovi, labelling appropriately.
2. Do a chi-squared test to determine whether the recent use of analgesics differed across staff categories.
3. Summarise fully the results of the analysis and give your conclusion.

1. A new treatment for influenza was developed. Over 1500 elderly people who were susceptible to the disease were included in the study. The table below gives the results of the study
 Influenza Healthy Treatment 25 752 Placebo 72 720

Enter the data into jamovi, label and set measure type appropriately. Ensure the rows and columns are in the correct order. Then in jamovi:

1. Obtain the odds ratio for these data.
2. Obtain the 95% confidence interval for the odds ratio.
3. Summarise the results of your analyses from a) and b).
4. Obtain the relative risk for the data.
5. Give the result in terms of absolute risk, and calculate the absolute risk reduction.
6. Calculate the number needed to treat.