Question

Many boxed cake mixes include special high-altitude baking instructions. One would like to investigate that, on an average, cakes take longer to bake at high altitudes. A consumer group made several similar cakes in nine-inch rounded pans in Denver and Miami, and carefully recorded the time to bake (in minutes). The data is given as follows:

Baking Times at High Altitude 22.8 30.0 27.3 30.3 28.3 31.1 27.0 26.8 26.3 29.1 23.5 26.2 29.2 23.0

Baking Times at Low Altitude 25.1 25.6 24.9 23.7 25.5 22.4 24.7 24.2 25.6 24.8 23.9 24.4 24.7 24.4 26.4 24.7 24.7 26.8 24.9 24.3

(a)Draw side-by-side boxplots for low and high altitudes. Write a short description about what you observe from the boxplots by examining them individually and contrasting them with regard to measures of center, variability and shapes.

(b)Make a quantile-quantile plot of the data with a 45 degree line added to it. What does the plot tell you about the baking times at the low and high altitudes?

Answer 1

Result:

(a)Draw side-by-side boxplots for low and high altitudes. Write a short description about what you observe from the boxplots by examining them individually and contrasting them with regard to measures of center, variability and shapes.

Median of Baking Times at High Altitude is larger than Median of Baking Times at Low Altitude. Variability of Baking Times at High Altitude is larger than that of Baking Times at Low Altitude. Baking Times at High Altitude is negatively skewed while Baking Times at Low Altitude is positively skewed.

(b)Make a quantile-quantile plot of the data with a 45 degree line added to it. What does the plot tell you about the baking times at the low and high altitudes?

Points in the plot are around the 45 degree line.   Therefore the baking times at the low and high altitudes are approximately normally distributed.