Question 8.21

8.21 Soft drink consumption in New Zealand

A survey commissioned by the Southern Cross Healthcare Group reported that 16% of New Zealanders consume five or more servings of soft drinks per week. The data were obtained by an online survey of 2006 randomly selected New Zealanders over 15 years of age.7

  1. What number of survey respondents reported that they consume five or more servings of soft drinks per week? You will need to round your answer. Why?
  2. Find a 95% confidence interval for the proportion of New Zealanders who report that they consume five or more servings of soft drinks per week.
  3. Convert the estimate and your confidence interval to percents.
  4. Discuss reasons why the estimate might be biased.

8.21

(a) . We need to round because you can’t have .96 of a person, so . (b) (0.144, 0.176). (c) (14.4%, 17.6%). (d) Because the numbers are self-reported, those who responded could be more or less likely to discuss their soft-drink consumption than those who didn’t respond.