Question

In a sample of 800 students the mean weight and standard deviation of weight are found to be 50 kg and 20 kg respectively . On the assumption of normality what is the number students weighing between 46 kg and 62 kg ?

Answer 1

Explanation:

I'll give you two approaches to answer this question. The first approach is how I would answer this in a school assignment or examination. The second approach is how I would find the answer quickly in my mind:

First approach:

Recalling this definition:

Mean=TotalNumber of samples

Use this on all the numbers you see in the question and you get enough material to find the answer.

Mean weight of students (M)=Total weight of students (W)Number of students (N)

Mean weight of boys (Mb)=Total weight of boys (Wb)Number of boys (Nb)

Mean weight of girls (Mg)=Total weight of girls (Wg)Number of girls (Ng)

So we get

60=W150

70=WbNb

55=WgNg=W−Wb150−Nb

So we get three linear equations with three variables, W , Wb , Nb to solve for. I'll let you complete the rest for your assignment