A company introduced a new pay structure for manual employees, the aim being to reward higher productivity. After the pay structure had been working for some time, a random sample of manual employees was selected. The number of items they produced per hour is given below:

46 57 41 65 48 63 51 50 43 54 47 59

In the past the average number of items produced per hour by the labor force was 48 items per hour. Test to see if the productivity has increased. (Significance level = 5%).