Question

Imagine the average time to complete a “4-year” bachelors degree is actually 4.3 years based on national data. You collect data on the 20 psychology students who started school during the same semester as you, finding an average time to complete at 4.5 years, with a sample standard deviation of 0.5 years. What is your 95% confidence interval? (for your FINAL answers, round to the nearest TWO decimal places)

Answer 1

To answer you question, we need the confidence internals formula, μ±Zc*(σ/
`√(N)`); N is the 20 psychology students, 0.5 the desviation standar and 4.3 is the medium based on national data, every fact in years.

Explanation:

You need to consult the Zc value, you can find this table attached in this question; for 95%, we have a Zc value of 1.96.

Next step replace values: 4.3±1.96*(0.5/
`√(20)`) = 4.3±0.22 (rounding the result)

So, the confidence interval are:

4.08cm≤X≤4.52cm