The average prices for a product in 12 stores in a city are shown below.
$2.99, $2.15, $3.25, $3.55, $3.00, $2.99, $2.66, $3.50, $3.20, $2.15, $3.75, $3.85
Test the hypothesis that the average price is higher than $2.57. Use level of significance a = 0.05.