Exercises on Measures of Central Tendency Enter There

Exercises on Measures of Central Tendency Enter

There are seven multiple-choice questions in this exercise. Click the letter to select the corresponding answer. Enter

1. This is the frequency distribution of the ages of students in a class. Age Frequency 11 7 12 19 13 10 14 4 Find out their mean age. A 12 B 12. 3 C 12. 5 D 19

Age Frequency 11 12 13 14 7 19 10 4 Mean age Bingo！ Next question

12 is the mode, not the mean. Try again！ Hints: Age Frequency 11 12 13 14 7 19 10 4 Mean age Return

Sorry! You forgot to count the frequencies! Try again! Hints: Age Frequency 11 12 13 14 1 1 Mean Age Frequency 11 12 13 14 7 19 10 4 Mean age = ? Return

19 is the frequency of 12 year-old. That means there are 19 students who are 12 years old. You should be looking for the mean of the students’ age. Try again! Hints: Age Frequency 11 12 13 14 7 19 10 4 Mean age Return

2. This is the frequency distribution of the weights of 50 members of a children’s choir. Weight（kg） Class mark, x kg 36 -40 41 -45 46 -50 51 -55 56 -60 61 -65 Find out their mean weight. A 50. 5 kg B 51. 8 kg C 56 -60 kg 38 43 48 53 58 63 Frequency 2 8 11 12 13 4

Mean weight (kg) Bingo！ Next question

56 -60 kg is the modal class, not the mean weight. Try again! Hints： Weight（kg） Class mark, x kg Frequency 36 -40 41 -45 46 -50 51 -55 56 -60 61 -65 38 43 48 53 58 63 2 8 11 12 13 4 Mean weight Return

Sorry! You forgot to count the frequencies. Try again! Hints： Weight Frequency Mean weight Weight（kg） Class mark, x kg Frequency 36 -40 41 -45 46 -50 51 -55 56 -60 61 -65 38 43 48 53 58 63 2 8 11 12 13 4 Mean weight= ? Return

3. The table shows the number of mobile phones owned by 100 families. Number of mobile phones 2 3 4 5 6 7 Find the mode. A 4 B 4. 5 C 5 38 D Frequency 2 6 38 16 20 18

Bingo！ Mode is the most frequent datum/data in a set of data. Therefore: Mode = 4 Next question

5 is the mean of mobile phones owned by each family, not the mode. Try again! Hints： Mode is the most frequent datum/data in a set of data. Return

38 is the frequency of 4. That means there are 38 families that have 4 mobile phones. You should be looking for the mode！ Try again! Hints： Mode is the most frequent datum/data in a set of data. Return

Sorry, your answer is wrong. Try again! Hints： Mode is the most frequent data in a set of data. Return

4. This is the frequency distribution of the time spent by Kelly on waiting for the bus last week. Time (minutes) Class mark (minutes) 1 -5 6 -10 11 -15 16 -20 21 -25 3 8 13 18 23 Find the modal class. A 6 -10 minutes B 8 minutes C 12. 9 minutes D 11 -15 and 16 -20 minutes Frequency (days) 0 15 12 12 1

Bingo！ Modal class is the most frequent class in a set of data. Therefore: Modal class = 6 -10 minutes Next question

12. 9 is the mean of the time spent on waiting for the bus, not the modal class. Try again! Hints： Modal class is the most frequent class in a set of data. Return

8 is the class mark of the class “ 6 -10 minutes”. You should be looking for the modal class of the time spent by Kelly on waiting for the bus in the past 40 days. Try again! Hints： Modal class is the most frequent class in a set of data. Return

Sorry, your answer is wrong. Try again! Hints： Modal class is the most frequent class in a set of data. Return

5. This is the frequency distribution of the time spent by 80 students in finishing a 3, 000 -meter track. Time（minutes） Class mark (minutes） Frequency (No. of person) 10 -15 16 -20 21 -25 26 -30 31 -35 13 18 23 28 33 4 9 14 14 9 Find the modal class. A 15. 3 minutes B 16 -20 and 31 -35 minutes C 21 -25 and 26 -30 minutes

Bingo！ Modal class is the most frequent class in a set of data. Therefore: Modal class = 21 -25 and 26 -30 minutes Next question

15. 3 minutes is the mean of the time needed to finish a 3, 000 -meter track, not the modal class! Try again! Hints： Modal class is the most frequent class in a set of data. Return

Sorry, your answer is wrong. Try again! Hints： Modal class is the most frequent class in a set of data. Return

6. This is the cumulative frequency polygon of the salaries of a company’s employees. Find the median. 100 90 80 Cumulative frequency (person) A 15000 dollars B 15400 dollars C 15800 dollars 70 60 50 40 30 20 10 0 5000 7000 9000 11000 13000 15000 17000 19000 21000 23000 25000 Salary (dollars)

Bingo！ Since there are 90 employees in the company, there median can be found at the 45 th employee. Therefore: Median=15000 dollars Next question

Sorry, you didn’t pay attention to the cumulative number of employee. Hints： Since there are 90 employees in the company, there median can be found at the 45 th employee. Try again! Return

7. This is the cumulative frequency polygon of rainfall in Island West during the past 40 days. Find the median. 45 A 20 mm 40 35 Cumulative frequency (day) 30 25 20 70 mm C 77 mm D 85 mm 15 10 5 0 B 20 40 60 80 Rainfall amount (mm) 100 120

Bingo！ The median of rainfall in 40 days can be found at the 20 th day. Therefore: Median = 70 mm End

Sorry, you didn’t pay attention to the cumulative number of days. Try again! Hints： The median of rainfall in 40 days can be found at the 20 th day. Return

The End