Section 3.1 Measures of Central Tendency

(HW: add #4, 5, 6, 36, 42 from text )

EX: Grades 81 68 72 76 94 56 85 80 72 74 63 90

a. Determine the mean grade (round to one more place than the raw data).

b. Randomly select one score and write it down (see p.29 on using calculator to randomize).

c. Take a random sample of four scores and find the sample mean (

(see p.29 on using calculator to randomize) ______

______EX: Arrange the scores above in order, then find the median. Grades 81 68 72 76 94 56 85 80 72 74 63 90

______EX: 1, 1, 1, 2, 10 Find the mean and median

______EX: 1, 4, 10, 10, 10 Find the mean and median

______Guidelines (continuous data, not discrete) – p. 132 [sketch bell-shaped, skewed right, skewed left and compare mean and median] Bell-shaped: μ ≈ M Skewed right: μ > M Skewed left: μ < M

______EX: (p. 138, #28) Length of eruption (in seconds) for Old Faithful geyser in Calistoga, California. 108 108 99 105 103 103 94 102 99 106 90 104 110 110 103 109 109 111 101 101 110 102 105 110 106 104 104 100 103 102 120 90 113 116 95 105 103 101 100 101 107 110 92 108

Find the mean and median.

______

______EX: Find the mode for the grades given earlier: Grades 81 68 72 76 94 56 85 80 72 74 63 90

______bimodal multimodal ______EX: Two small companies each have ten employees, with the hourly wages shown. Compare the mean, median and mode for these companies. Company A: 8, 8, 8, 8, 8, 8, 8, 8, 20, 500 Company B: 8, 8, 8, 8, 20, 20, 500, 500, 500, 500

______

Reminder: Mean Median - ‘middle’ Mode - ‘most’