Normal Distribution

Question 1

What factors contribute to normal distribution

Answer 1

Many factors contribute. Someone will have more of one factor and less of another. Random combinations of factors. Often a high factor and a low factor will cancel giving a more average outcome. More rare to have a lot of high factors coming together. Likewise rare to have a lot of low factors. Hence much bunching around the middle and fewer values at the extremes.

Question 2

What is the difference between population mean and sample mean

Answer 2

Population mean, is what we are trying to measure. Sample mean, is what we get from a survey. It is an estimate of . If you took many samples, their means would be distributed around with standard deviation . Sample mean varies because of randomness of which individuals are in the sample. Sometimes more values to the high side giving a high value of . Likewise on the low side.

Question 3

What % of data fall within 1st SD of the mean

Answer 3

68%

Question 4

What % of data fall within 2nd SD of the mean

Answer 4

95%

Question 5

What % of data fall within 3rd SD of the mean

Answer 5

99.7%