Example 1.4 presented data on the starting salaries of n = 38 civil engineering graduates. Use this data to construct a 95% confidence interval for the population lower quartile (25th percentile) of civil engineering starting salaries.

Example 1.4

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Example 1.4 Job prospects for students majoring in an engineering discipline continue to be very robust. How much can a new engineering graduate expect to earn? Here are the starting salaries for a sample of 38 civil engineers from one author's home institution (Spring 2016), courtesy of the university's Graduate Status Report: 58,000 62,000 56,160 67,000 66,560 65,000 60,000 61,000 80,000 62,500 55,000 63,000 60,000 70,000 55,000 52,000 70,000 80,000 60,320 65,000 70,000 65,000 58,240 60,000 75,000 60,000 72,000 83,000 61,000 70,000 61,000 68,000 57,600 65,000 56,000 63,000 68,640 50,128 Figure 1.3 shows a stem-and-leaf display of these 38 starting salaries. Hundreds places and lower have been truncated; for instance, the lowest salary in the sample was $50,128, which is represented by 50 in the first row. 5L 02 SH 5566788 6L 6H 000001112233 55556788 7L 00002 7H 5 8L 003 Stem: $10,000 Leaf: $1000 Figure 1.3 Stem-and-leaf display for starting salaries of civil engineering graduates