If the number is a multiple of 8, it is divisible by 8. The multiples of 8 are: 8, 16, 24, 32, 40, 48, 56, 64, 72, 80, 88... etc.
If a number is very big, let's say 176, see if you can deduct 80 from it. For this, 176 can be deducted by 80 twice, which will give you a remainder of 16 (I.e. 176 - 80 - 80 = 16". If this remainder (i.e. 16) is divisible by 8, 176 is divisible by 8.
For even larger numbers, try deducting 800, or even 8000.
Let's say you're trying to see if 2464 is divisible by 8. In this case, 2464 can be deducted by 800 thrice (I.e. 2464 - 800 - 800 - 800 = 64), and 64 is its remainder. Since 64 is divisible by 8, 2464 is divisible by 8.
We can find critical value by using t - table. For using t - table we need degree of freedom and alpha either for two tailed test or one tailed test. We can determine degree of freedom by subtracting sample size from one. So in given question sample size is 23. So we can say degree of freedom(df) for sample size 23 is df = 23 - 1= 22 Now we have to go on row for degree of freedom 22.
After that we need to find alpha either for two tailed test or one tailedl test. Confidence level is 99%. We can convert it into decimal as 0.99.
So alpha for two tailed test is 100 - 0.99 = 0.01
Alpha for one tailed test is 0.01/2 = 0.005.
So we will go on column for 0.01 for two tailed test alpha or 0.005 for one tailed test alpha. SO the critical value 22 degree of freedom and 0.01 two tailed alpha is 2.819 from t - table.
