A researcher investigated the impact of sleep duration on cognitive performance using an independent groups design. She used a directional hypothesis and analysed the interval-level score data using an unrelated t-test. The calculated value of $t$ where degrees of freedom ($df$) = 14 was 1.825. She decided to use the 5% level of significance.

Give three reasons why the researcher used an unrelated t-test in this study and, using Table 1, explain whether or not the results are significant.

Table 1: Critical values of t

Note: The calculated value of t must be equal to or greater than the critical value in this table for significance to be shown.