Question

3. Construct a 98% confidence interval estimate for the mean μ using the given sample information. (Give your answers correct to two decimal places.)

n = 26, x = 18, and s = 2.7

Answer 1

So to find the 98% conf interval we need to find z value from the normal distribution curve for 1% area towards left and 1% area towards right

So the z value is -2.326 for left end 1% area and +2.326 for right 1% area from z table

Now using the formula

μ = x + z* s/sqrt(n)

so., μ_lower = 18 -2.326*2.7/sqrt(26)=16.76835

and μ_upper = 18 +2.326*2.7/sqrt(26) = 19.23165

Hence we can say that 98% conf interval for μ is from 16.76835 to 19.23165

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