Answer:
Since, 113 is on the confidence interval obtained (97.502, 114.098), so, we can suggest that is plausible that the true average IQ score for all seventh-grade female students at this school is 113.
Explanation:
The question isn't complete, the missing part asked us to obtain a 99.5% confidence interval for the true average IQ score
Finding the confidence interval using the sample data provided, we can answer the question of plausibility.
Confidence Interval for the population mean is basically an interval of range of values where the true population mean can be found with a certain level of confidence.
Mathematically,
Confidence Interval = (Sample mean) ± (Margin of error)
Sample Mean = 105.8
Margin of Error is the width of the confidence interval about the mean.
It is given mathematically as,
Margin of Error = (Critical value) × (standard Error of the mean)
Critical value will be obtained using the t-distribution. This is because there is no information provided for the population mean and standard deviation.
To find the critical value from the t-tables, we first find the degree of freedom and the significance level.
Degree of freedom = df = n - 1 = 31 - 1 = 30
Significance level for 99.5% confidence interval
(100% - 99.5%)/2 = 0.25% = 0.0025
t (0.0025, 30) = 3.03 (from the t-tables)
Standard error of the mean = σₓ = (σ/√n)
σ = standard deviation of the sample = 15
n = sample size = 30
σₓ = (15/√30) = 2.739
99.5% Confidence Interval = (Sample mean) ± [(Critical value) × (standard Error of the mean)]
CI = 105.8 ± (3.03 × 2.739)
CI = 105.8 ± 8.298
99.5% CI = (97.502, 111.387)
99.5% Confidence interval = (97.502, 114.098)
Since, 113 is on the confidence interval obtained, so, we can suggest that is plausible that the true average IQ score for all seventh-grade female students at this school is 113.
Hope this Helps!!!