A different sample of size n = 20 produced a sample mean of 31.08% and a sample standard deviation of 5.48%. Use these values to calculate a 90% confidence interval for the national mean percent of low-income working families. Please show all calculations and provide the upper and lower limits that make up the confidence interval. (Round the limits to two decimal places).
A random sample of size n = 20 which produced a sample mean of 31.08% and sample standard deviation of 5.48%.
Thus n = 20 , , s = 5.48
We have to find 90% confidence interval for the national mean percent of low income working families.
Since sample size = n = 20 is small and population standard deviation = is unknown.
Thus we use t distribution to find confidence interval.
Formula for confidence interval for mean is :