Oxford-AstraZeneca Vaccine: Why the Uncertainty?

The preliminary results from phase III trials of COVID-19 vaccines have been reported in the media. The vaccine developed and trialled by Pfizer and BioNTech is reported to be 95% effective and Moderna's is 94.5% effective. Trial results of the vaccine being developed by Oxford University and AstraZeneca show that it is 70% effective, but "with potential for that to rise to 90 per cent". In this blog we explore the reasons and implications of this uncertainty.

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Assessing Questionnaire Reliability

Questionnaire surveys are a useful tool used to gather information from respondents in a wide variety of contexts. We invariably use surveys because we want to measure something, for example, how frequently people exercise, voting intentions, the percentage of your customers that would recommend you to a friend. As such surveys can be viewed as a measurement instrument of, for example, behaviours, attitudes and opinions. Two important qualities of surveys, as with all measurement instruments, are consistency and accuracy. These are assessed by considering reliability and validity - in this blog we consider reliability.

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Why Use a Complex Sample for Your Survey?

Most statistical analyses assume that the data collected are from a simple random sample of the population of interest. However, it’s not always possible or practical to take a SRS, and complex samples can be used to create more efficient or cheaper sampling designs.

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