A car manufacture produces a new car that advertises an average of 30 MPG. The distribution of MPG of cars is normally distributed. The manufacturer will test 30 cars off the assembly line to find a confidence interval of the average MPG of their new vehicle to determine if it is close to 30. The average MPG of the 30 cars is 31.2 gallons with a standard deviation of 2 gallons. Find a 95% confidence interval for the average MPG of the new vehicle.
Added by Stacy W.
Step 1
The formula for a confidence interval is: X̄ ± Z * (σ/√n) where: X̄ is the sample mean, Z is the Z-score (which corresponds to the desired confidence level, in this case, 95%), σ is the standard deviation, and n is the sample size. Show more…
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