STA 301 - HW02 Key

# STA 301 - HW02 Key - STA 301 Applied Statistics Spring 2008...

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2.0 2.1 2.2 2.3 2.4 2.5 Tensile Strength Megapascals Curing Temperature 45C 20C STA 301 – Applied Statistics Spring 2008, Section B Homework #2 - Key Due Wednesday, February 6 PART I – Paper-and-pencil problems Question 1 : (p. 14, #1.6 modified): The tensile strength of silicone rubber is thought to be a function of curing temperature. A study was carried out in which samples of 12 specimens of the rubber were prepared using curing temperatures of 20°C and 45°C. The data below show the tensile strength values in megapascals. 2.07 2.14 2.22 2.03 2.21 2.03 20°C 2.05 2.18 2.09 2.14 2.11 2.02 2.52 2.15 2.49 2.03 2.37 2.05 45°C 1.99 2.42 2.08 2.42 2.29 2.01 (a) Construct dot plots for the two data sets. (Stack the dot plots, using the same scale for each.) (b) Without calculating anything, comment on the apparent relationship between curing temperature and the following aspects of tensile strength: Mean The mean tensile strength is higher at the higher curing temperature. Variance The tensile strength has higher variance at the higher curing temperature.

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STA 301-B, Spring 2008 Homework 2 Key Page 2 of 6 Presidential Children Number of Children Relative Frequency (.190) (.357) (.238) (.143) (.024) (.024) (.024) 0-1 2-3 4-5 6-7 8-9 10-11 12-13 14-15 0 0.1 0.2 0.3 Question 2 The Information Please Almanac provides the number of children of each of the 42 U.S. presidents. The data are provided below. 0 5 6 0 2 4 0 4 10 15 0 6 2 3 0 4 5 4 8 7 3 5 3 2 6 3 3 0 2 2 6 1 2 3 2 2 4 4 4 6 1 2 (a) Create a grouped data table for these data, using classes 0-1, 2-3, 4-5, … 14-15. Number of Children Frequency Relative Frequency Midpoint 0-1 8 .190 0.5 2-3 15 .357 2.5 4-5 10 .238 4.5 6-7 6 .143 6.5 8-9 1 .024 8.5 10-11 1 .024 10.5 12-13 0 .000 12.5 14-15 1 .024 14.5 Total 42 1.000 (b) Construct a relative frequency histogram based on the grouped data table from part (a).
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