Collecting data

Explain one problem of using an online survey to find out about the internet use of older people.

A town has the following numbers of adult residents (data are illustrative, written for this paper): Under 25: 240 | 25–44: 360 | 45–64: 300 | 65+: 100. A stratified sample of 50 residents is taken. Calculate how many residents aged 25–44 should be in the sample.

Explain the difference between a census and a sample survey, and give one reason for using a sample.

Raw data from a survey of students' ages and hours of sleep (data are illustrative, written for this paper): (15, 8), (16, 7.5), (14, 9), (61, 7), (15, 28), (16, 8.5). Identify two values that should be checked or removed when cleaning the data, giving reasons.

Which of these is a random sampling method?

Describe how to select a quota sample of 40 people (20 male, 20 female) in a town centre and give one disadvantage.

Ecologists catch and tag 30 squirrels in a wood. A week later they catch 36 squirrels, of which 6 are tagged. Use the Petersen capture–recapture method to estimate the population.

State one assumption made in using this method.

Explain how to reduce non-response in a postal survey.

Raw data from a survey of students' ages and hours of sleep (data are illustrative, written for this paper): (15, 8), (16, 7.5), (14, 9), (61, 7), (15, 28), (16, 8.5). Identify two values that should be checked or removed when cleaning the data, giving reasons.