• Option 2 – Observational Data handling and Analysis.

(a) 200 children aged under 5 years were sampled from a village in Malawi using simple random sampling. All of the children were tested for malaria using a rapid diagnostic test. 51 of the children tested positive. Estimate the prevalence of malaria in children under 5 years old in the village and provide a 95% confidence interval for the estimate.

• Make sure you read the questions thoroughly

• Think about what the question is asking you to calculate first.

• Think about what is required in a CI calculation

• Summarize you findings for clarity

(b) 40% of children had slept under a bed net the night before the survey. Of these 15% tested positive for malaria.

• (i) Construct a carefully labeled two-way table for the data derived from the 200 children.

• Think about the layout of the table exposure vs outcome

• (ii) Estimate the odds ratio, risk ratio and risk difference for those who did not sleep under a bed net the night before compared to those that did.

• Use your lecture notes for the equations

• (iii) A statistician performed a x2 test and obtained a p-value of 0.005. Interpret this result.

(c) • It has been suggested that families of higher socio-economic status are more likely to own bed nets and are also more likely seek malaria treatment when they are ill. Families have been grouped into three categories of socio economic status.

• (i) Suggest a statistical technique that would let us examine the association between bed net use and malaria infection taking into account the differences in socio economic status.

• (ii) Which of the three measures of association mentioned in part (b) will this technique produce?

• (iii) Is the adjusted estimate likely to be closer to or further away from the null value than the unadjusted estimate from part (b)(ii)? Give a brief explanation for your answer.

• Socio economic status considered a confounder here