Notes

1-Write down the phenomenon you'd like to test. Let's say you're working with the following situation: The average height of a male student in School is 180cm. You'll be testing how accurately you will be able to predict the height of male students in School within a given confidence interval.
2-Select a sample from your chosen population. This is what you will use to gather data for testing your hypothesis. Let's say you've randomly selected 2000 male students.
3-Calculate your sample mean and sample standard deviation. Choose a sample statistic
• To calculate the sample mean of the data, just add up all of the heights of the 2000 students you selected and divide the result by 2000. This should have given you the average height of 180cm
• To calculate the sample standard deviation, you will have to find the mean, of the data. Next, you'll have to find the variance of the data of the squared differences from the mean. Once you find this number, just take its square root. Let's say the standard deviation here is 30cm
4-Choose your desired confidence level. Let's say you've chosen 95%.
5-Calculate your margin of error. You can find the margin of error by using the following formula: Za/2 * σ/√(n). Za/2 = the confidence coefficient, where a = confidence level, σ = standard deviation, and n = sample size.
To find the critical value, or Za/2: Here, the confidence level is 95%. Convert the percentage to a decimal, .95, and divide it by 2 to get .475. Then, check out the z table to find the corresponding value that goes with .475. You'll see that the closest value is 1.96, at the intersection of row 1.9 and the column of .06.
To find the standard error, take the standard deviation, 30, and divide it by the square root of the sample size, 2000 You get 30/44.7
Multiply 1.96 by 0.67 to get 1.3 your margin of error.