A shoemaker claims his best product has an average lifespan of exactly 14 years. A skeptical customer asks for evidence (data) that might be used to evaluate this claim. The customer was provided data collected from a random sample of 45 people who used the product. Using the data, an average product lifespan of 15 years and a standard deviation of 6 years was calculated. Select the 95%, confidence interval for the true mean lifespan of this product.
a) [14.739, 15.261]
b) [13.247, 16.753]
c) [12.317, 17.683]
d) [12.247, 15.753]
e) [-1.7531, 1.7531]
f) None of the above
An important problem in industry is shipment damage. A pottery producing company ships its product by truck and determines that it cannot meet its profit expectations if, on average, the number of damaged items per truckload is greater than 11. A random sample of 15 departing truckloads is selected at the delivery point and the average number of damaged items per truckload is calculated to be 11.3 with a calculated sample of variance of 0.64. Select a 90% confidence interval for the true mean of damaged items.
a) [10.68, 11.92]
b) [10.64, 11.36]
c) [53.67, -33.86]
d) [-0.3635, 0.3635]
e) [10.94, 11.66]
f) None of the above