A random sample of 20 houses selected from a city showed that the mean size of these houses is 1880 square feet with a standard
deviation of 320 square feet. Assume that the sizes of all houses in this city have an approximate normal distribution. The upper bound the 90% confidence interval for the mean size of all houses in this city is: A. 2110 B. 1941 C. 1974 D. 1968 E. 1894
Given that for a random sample of 20 houses selected from a city showed that the mean size of these houses is 1880 square feet with a standard deviation of 320 square feet.
X, the sizes of houses is Normal
Hence sample mean will be normal with
Mean = 1880
and std dev =
For 90% confidence interval critical value for t with degree of freedom 19 is