Does anyone know of an easy way to identify the Null Hypothesis in word questions? I find that sometimes it's the sample mean and others it's the population mean. Take the following for example:
A local manufacturer of doors for use in home construction is attempting to determine if the average height of adult males in it's market area has changed from 70 inches. A sample of 121 men was randomly selected. The average height was found to be 72 inches with a standard deviation of 2 inches. At the 0.05 significance level, can we conclude that the mean height has changed?
I thought that Ho:u=70 (the population mean) but it turns out to be 72 (the sample mean). Why?