(a)[3]
The survey showed that 102 adults in the sample travel by bus. Calculate an approximate $90\%$ confidence interval for the proportion of all adults in Fromleigh who travel by bus.
(b)[3]
The survey asked about the yearly amount, $x$ dollars, spent on travel. The summary is $n = 250$, $\sum x = 50\,460$, $\sum x^2 = 19\,854\,200$. Find unbiased estimates of the population mean and the variance of the amount spent on travel per year.
(c)[1]
A councillor wanted to draw a random sample of houses in Fromleigh. He intended to choose the first house on each of the 143 streets in Fromleigh. Explain why this would not produce a random sample.