Case Study: The “Chip Ahoy! 1,000 Chips Challenge (p. 357): Answer a, b, c, e (NOT d, but you should read Question d as it gives you hints to solve Question e). You must calculate results by hand (though you may use any technology of your choice to verify your answers).
a. Obtain and interpret a point estimate for the mean number of chocolate chips per bag for all bags of Chips Ahoy! Cookies.
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Normal Probability Plot: The data in the attached chart shows a straight diagonal line and this shows that the chips are distributed normally across the 42 bags of Chips Ahoy! Cookies tested.
Box Plot: This shows the median (1241.5) in the center of the grey area of the box. The box upper and lower edges show the above 75% and below 25% of the data with the range between being the IQR. The small circle at the top shows the potential outliers (1514, 1545, and 1546).
Histogram: The data in the histogram shows the largest chip count is between 1100-1300 chips. The potential outliers are located on the right, above 1500 chips.
c. Use the graphs in part (b) to identify outliers, if any.
The outliers are the chip totals of 1514, 1545, and 1546.
e. Determine a 95% confidence interval for the mean number of chips per bag for all bags of Chips Ahoy! Cookies, and interpret your results in words.
The sample mean is 1261.6, standard deviation is 117.6.
1261.6 + 117.6 = 1379.2
1261.6 – 117.6 = 1144
95% of the number of chips per bag are between 1144-1379