In: Statistics and Probability
7. Use the population of {1, 3, 7}. Assume that the random samples of size n = 2 Construct a sampling distribution of the sample mean. After identifying the 9 different possible samples (with replacement), find the mean of each sample, then construct a table representing the sample the sampling distribution of the sample mean. In the table, combine values of the sample mean that are the same. (Hint: condense the table similar to examples presented in class.)
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We have the population {1,3,7}.
Let x1, x2, ..., xn be a random sample of size n.
Then the sample mean is given by the formula
.
Here, since we are taking sample of size 2, say x1 and x2, the sample mean can be obtained as

case (i): Random sample of size 2 with replacement.
The following are the possible samples with their corresponding sample means.
| Samples (with replacement) |
Sample means |
| {1,1} | 1 |
| {1,3} | 2 |
| {1,7} | 4 |
| {3,1} | 2 |
| {3,3} | 3 |
| {3,7} | 5 |
| {7,1} | 4 |
| {7,3} | 5 |
| {7,7} | 7 |
Therefore the sampling distribution of sample mean is obtained as in the following table.
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| 1 | 1/9 |
| 2 | 2/9 |
| 3 | 1/9 |
| 4 | 2/9 |
| 5 | 2/9 |
| 7 | 1/9 |
case (ii): Random sample of size 2 without replacement. (mentioned additionally, not asked in the question)
The following are the possible samples with their corresponding sample means.
| Samples (without replacement) |
Sample means |
| {1,3} | 2 |
| {1,7} | 4 |
| {3,7} | 5 |
Therefore the sampling distribution of sample mean is obtained as in the following table.
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| 2 | 1/3 |
| 4 | 1/3 |
| 5 | 1/3 |