The statistics do seem to indicate that gifts are less used than purchased items. However,
a further statistical measure needs to be applied to see if this difference is statistically
significant. Table 4 shows how the two equal-sized groups were broken down so that at-test
could measure the difference between the means (0.87 for gifts and 1.38 for non-gifts). An
important piece of information for calculating the t-value is the square of the distance from
the mean for each book in both groups. Table 4 shows the sum of these squares (248.08 for
non-gifts and 126.7 for gifts). From the data in Table 4, information needed to calculate the
t-value is derived (Table 5). Figure 1 shows the formula for calculating the t-value.
Substituting the values in Table 5 into this formula at-value of 2.00 is established. With 76
degrees of freedom (k21), the value demanded for significance at the 0.05 level is 1.99.
Because thet-value in this study is 2.00, it is determined that there is a significant difference
at the 0.05 level. Therefore, it is accurate to state that gift books were used significantly less
than non-gift books in this study.