Answer:
(a) The point estimate of the population mean HDL cholesterol level is 49.95.
(b) The point estimate of the value that separates the largest 50% of HDL levels from the smallest 50% is 47.5.
(c) The point estimate of the population standard deviation is 16.85.
Step-by-step explanation:
We are given a sample of 20 observations on HDL cholesterol level (mg/dl) obtained from the survey below;
35, 49, 51, 54, 65, 51, 52, 47, 87, 37, 46, 33, 39, 44, 39, 64, 94, 34, 30, 48.
(a) The point estimate of the population mean HDL cholesterol level is given by the sample mean of the above data, i.e;
Sample Mean,
=
=
=
= 49.95
So, the point estimate of the population mean HDL cholesterol level is 49.95.
(b) The point estimate of the value that separates the largest 50% of HDL levels from the smallest 50% is given by the Median of the above data.
Firstly, arranging the given data in ascending order we get;
30, 33, 34, 35, 37, 39, 39, 44, 46, 47, 48, 49, 51, 51, 52, 54, 64, 65, 87, 94.
Now, for calculating median we have to first observe that the number of observations (n) in our data is even or odd, i.e;
- If n is odd, then the formula for calculating median is given by;
Median =
- If n is even, then the formula for calculating median is given by;
Median =
Here, the number of observations is even, i.e. n = 20.
So, Median =
= ![\frac{(\frac{20}{2})^{th} \text{ obs.}+(\frac{20}{2}+1)^{th} \text{ obs.} }{2}](https://tex.z-dn.net/?f=%5Cfrac%7B%28%5Cfrac%7B20%7D%7B2%7D%29%5E%7Bth%7D%20%5Ctext%7B%20obs.%7D%2B%28%5Cfrac%7B20%7D%7B2%7D%2B1%29%5E%7Bth%7D%20%5Ctext%7B%20obs.%7D%20%20%7D%7B2%7D)
=
=
Median = 47.5
Hence, the point estimate of the value that separates the largest 50% of HDL levels from the smallest 50% is 47.5.
(c) The point estimate of the population standard deviation is given by the following formula;
Standard deviation, s =
=
= 16.85