# Question: in order to estimate the speaking vocabulary of threeyearold children...

###### Question details

In order to estimate the speaking vocabulary of three-year-old
children in a particular socioeconomic class, a sociologist studies
the speech of four children. The mean and standard deviation of the
sample are x^{-} =1120 and *s* = 215 words. Assuming that
speaking vocabularies are normally distributed, construct an 80%
confidence interval for the mean speaking vocabulary of all
three-year-old children in this socioeconomic group.