Measures of Central Tendency

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Measures of Central Tendency:

Measures of Central Tendency Mean, Median, Mode, Range

Mean = Average:

Mean = Average Ex: Scott took 7 math tests this marking period. What is the mean test score? 89,  73,  84,  91,  87,  77,  94 The sum of these numbers is 595. Divide the sum by the # of test scores. The mean test score is 85.

Definition: :

Definition: The mean of a set of data is found by taking the sum of the data, and then dividing the sum by the total number of values in the set. The mean is the AVERAGE.

EX 2:

EX 2 Find the mean swimming time rounded to the nearest tenth : 2.6 min, 7.2 min, 3.5 min, 9.8 min, 2.5 min 2.6 + 7.2 + 3.5 + 9.8 + 2.5 = 25.6 25.6 ÷ 5 = 5.12 The mean swimming time to the nearest tenth is 5.1 min.

Median = middle #:

Median = middle # EX: The Doran family has 5 children, aged 9, 12, 7, 16 and 13. What is the age of the middle child? Order the ages from least to greatest: 7,  9, 12, 13,  16 The age of the middle child is the middle number in the data set, which is 12.

Definition::

Definition: The median of a set of data is the middle number in the set. To find the median, the data must be arranged in order.

EX 2:

EX 2 During the first marking period, Nicole's math quiz scores were 90, 92, 93, 88, 95, 88, 97, 87, and 98. What was the median quiz score? Order data from least to greatest 87,  88,  88,  90, 92 ,  93,  95,  96,  98 The median quiz score was 92.

What if there is an even number of items in the data set?:

What if there is an even number of items in the data set? EX: A marathon race was completed by 4 participants. What was the median race time? 2.7 hr,  8.3 hr,  3.5 hr,  5.1 hr Order data from least to greatest: 2.7, 3.5 , 5.1 ,  8.3 (continued…)

(continued):

(continued) Since there is an even number of items in the data set, we compute the median by taking the average of the two middle numbers. 3.5 + 5.1 = 8.6 8.6 ÷ 2 = 4.6 The median race time was 4.3 hr.

Mode:

Mode EX: The number of points scored in a series of football games is listed below. Which score occurred most often? 7,  13,  18,  24,  9,  3,  18 Order scores from least to greatest: 3,  7,  9,  13,  18,  18,  24 The score which occurs most often is 18.

Definition::

Definition: The mode is the scores (or scores) that appear most often. It is easiest to find the mode when the scores are listed in order.

Sometimes there is NO mode.:

Sometimes there is NO mode. EX: A marathon race was completed by 5 participants. What is the mode of these times given in hours? 2.7 hr,  8.3 hr,  3.5 hr,  5.1 hr,  4.9 hr Since each value occurs only once in the data set, there is no mode for this set of data.

There may be more than one mode:

There may be more than one mode EX: In a crash test, 11 cars were tested to find what impact speed would cause the least bumper damage. Find the mode of the speeds given in miles per hour below. 24,  15,  18,  20,  18,  22, 24,  26,  18,  26,  24 (continued)

(continued):

(continued) List in order: 15,  18,  18,  18,  20,  22,  24,  24,  24,  26,  26 Since both 18 and 24 occur three times, the mode s are 18 and 24 miles per hour.

Range:

Range The Smith family drove through 6 midwestern states on their summer vacation. Gasoline prices varied from state to state. What is the range of gasoline prices? $1.79,  $1.61,  $1.96,  $2.09,  $1.84,  $1.75 highest - lowest = $2.09 - $1.61 = $0.48

Definition::

Definition: The range of a set of data is the difference between the highest and lowest values in the set.

Review::

Review: What is the mean, median, mode, and range of the test scores listed below? 89,  93,  87,  86,  85,  94 Mean = 89 Median = 88 Mode = NONE Range = 9

Slide 18:

Instructions: Design a pizza for your group (3-4 people). Use a calculator to find the cost of your pizza. Write the cost of your pizza on the board.

Slide 19:

On the back of your pizza menu, find the MEAN, MEDIAN, MODE, and RANGE of the pizza prices listed on the board.