draw a simple random sample of 15 students from your class,and calculate sample mean and sample variance of their heights(use lottery method)
Find the mean first = sum of scores/number of scores
Subtract each of the scores from the mean and square each difference. Find the sum of these squares. Divide that by the number of scores to get variance.
To draw a simple random sample of 15 students from your class and calculate the sample mean and sample variance of their heights using the lottery method, you can follow these steps:
1. Assign a number to each student in your class. For example, if you have 30 students, number them from 1 to 30.
2. Use a random number generator, such as a random number table or an online random number generator, to select 15 unique random numbers between 1 and 30. Ensure that each number is selected independently and with equal probability.
3. Once you have the 15 random numbers, identify the corresponding students in your class based on their assigned numbers.
4. Measure the height of each of the 15 selected students using a measuring tool, such as a measuring tape or a height scale. Make sure to record the heights accurately.
5. Calculate the sample mean by adding up all the recorded heights and dividing the sum by the number of students in the sample (15). This will give you the average height of the sampled students.
6. Calculate the sample variance by following these steps:
a. Subtract the sample mean from each individual height measurement and square the result.
b. Sum up all the squared differences.
c. Divide the sum by the number of students in the sample minus 1 (in this case, 15-1=14). This will give you the sample variance.
Remember, using the lottery method ensures that every student in the class has an equal chance of being selected for the sample, helping to provide a representative sample of the entire class.