Use T-Statistic? Or use the Z value?

1. The local Tupperware dealers earned these commissions last month:

$4377.47 $3183.76 $1970.16 $2270.88 $3860.06

$2508.55 $1569.64 $4205.30 $1663.68 $3960.71

Assuming the population for the amount of commissions earned by Tupperware dealers last month is known to be normally distributed, create a 95% confidence interval estimate for , the mean amount of commission earned.

You will be asked to identify x-bar, s, alpha, df, t, E and the confidence interval.

My main Q here would be whether I would use Z statistic or I should use the T-statistic? also any idea on how to compute df?

Cheers

Darren