How can you tell if your sample means of a study will enable you to make a reliable prediction of the general population? please help im a braindead 13 year old who just wants to sleep

Use this data in the problem below. follow the steps carefully. round to the nearest tenth. lot 3: week 1: 345 week 2: 340 week 3: 400 week 4: 325 step 1. jim enters the data and calculates the average or mean. step 2. jim calculates the deviation from the mean by subtracting the mean from each value. step 3. jim squares each deviation to remove negative signs. step 4. jim sums the squares of each deviation and divides by the count for the variance. step 5. jim takes the square root of the variance to find the standard deviation.

Anyone know? will mark brainliest if you're correct!

Find an equation of the line perpendicular to the graph of 28x-7y=9 that passes through the point at (4,1)