can some 1 explain how do fa22020 become 2464 Thank you The

can some 1 explain how do fa/2,20.20 become 2.464

Thank you

The melting points of two alloys used in formulating solder were investigated by melting 21 samples of each material. The standard deviation for alloy 1 was s_1 = 4 degree F, while for alloy 2 it was s_2 = 3 degree F. Do the sample data support the claim that both alloys have die same standard deviation of melting point? Construct 95% confidence interval on sigma_1^2/sigma_2^2 to answer die question. 0.7214

Solution

f_a/2,20.20 is found by using F table.

Here a is nothing but level of significance i.e 0.05

Hence it becomes f_0.025,20,20

Here first d.f 20 is for numerator and second d.f. is for denominator.

Now in F table for level of significance 0.025, see across 20 ( numerator ) and 20(denominator), you will get 2.464.

Alternatively, you can use excel command :   =FINV(probability, degrees_freedom1, degrees_freedom2)

                                                                 i.e. = FINV(0.025,20,20)

You will get the answer!