Null hypothesis, Ho: m1- m2  = 0 Upper tail test Lower tail test Two tail test F Test

It seems like you're asking for explanations of several statistical testing terms. Here they are:

1. Null Hypothesis (Ho): This is a general statement or default position that there is no relationship between two measured phenomena, or no association among groups. In your case, Ho: m1 - m2 = 0 suggests that there is no difference between the two population means.

2. Upper Tail Test: This is a statistical test used to determine whether the critical value of the test statistic lies in the upper tail (right-hand side) of the distribution. It's used when the alternative hypothesis (H1) states that the parameter is greater than the null hypothesis value.

3. Lower Tail Test: This is the opposite of the upper tail test. It's used when the alternative hypothesis states that the parameter is less than the null hypothesis value.

4. Two Tail Test: This is used when the alternative hypothesis does not specify the direction of the difference or relationship. It tests for the possibility of the relationship in both directions.

5. F Test: This is a statistical test used to compare the variances of two populations. The null hypothesis for the F test is that the variances are equal. If the data significantly deviates from this, the null hypothesis is rejected.