Question

5. The superintendent of the local school district claims that the children in her district are brighter, on average, than the general population. To determine the aptitude of her district's children, a study was conducted. The results of her district's test scores were: 105, 109, 115, 112, 124, 115, 103, 110, 125, 99. If the mean of the general population of school children is 106, what could be said about her claim? Use alpha = .05

Answer 1

We conclude that children in district are brighter, on average, than the general population.

Explanation:

We are given the following data set:

105, 109, 115, 112, 124, 115, 103, 110, 125, 99

Formula:

`\text{Standard Deviation} = \sqrt{\displaystyle\frac{\sum (x_i -\bar{x})^2}{n-1}}`

where
`x_i` are data points,
`\bar{x}` is the mean and n is the number of observations.

`Mean = \displaystyle\frac{\text{Sum of all observations}}{\text{Total number of observation}}`

`Mean =\displaystyle(1117)/(10) = 111.7`

Sum of squares of differences = 642.1

`S.D = \sqrt{(642.1)/(49)} = 8.44`

We are given the following in the question:

Population mean, μ = 106

Sample mean,
`\bar{x}` = 111.7

Sample size, n = 10

Alpha, α = 0.05

Sample standard deviation, s = 8.44

First, we design the null and the alternate hypothesis

`H_(0): \mu = 106\\H_A: \mu > 106`

We use one-tailed(right) t test to perform this hypothesis.

Formula:

`t_(stat) = \displaystyle\frac{\bar{x} - \mu}{(s)/(√(n)) }`

Putting all the values, we have

`t_(stat) = \displaystyle(111.7 - 106)/((8.44)/(√(10)) ) = 2.135`

Now,

`t_(critical) \text{ at 0.05 level of significance, 9 degree of freedom } = 1.833`

Since,

`t_(stat) > t_(critical)`

We fail to accept the null hypothesis and reject it. We accept the alternate hypothesis.

We conclude that children in district are brighter, on average, than the general population.