Practice questions 7.3


1. A class want to raise money for their school trip. They are thinking about raising the money by selling raffle tickets. Before they decide to hold a raffle, they want to estimate how many students in the whole school would buy a ticket. They decide to do a survey to find out first.


The school has 900 students in first to sixth year with 150 students in each year. (i) How many students would you survey? How would you choose them? Explain your answers.


(ii) Sarah got the names of all 900 students in the school and put them in a hat. Then she pulled out one name, recorded it and replaced it. She did this 90 times. What do you think of Sarah’s sample selection? Explain your answer.


(iii) Jack asked 15 children at after-school study. What do you think of Jack’s sample selection? Explain your answer.


(iv) Adam asked all of the 150 students in first year. What do you think of Adam’s sample selection? Explain your answer.


(v) Ramon asked 90 of his friends. What do you think of Ramon’s sample selection? Explain your answer.


(vi) Caoimhe set up a stall outside the canteen. Anyone who wanted to stop and fill out a survey could. She stopped collecting surveys when she got 90 students to complete them. What do you think of Caoimhe’s sample selection? Explain your answer.


2. The table gives the height of roller coasters at an amusement park. Name of roller coaster Height (m)


Viper Monster


Red Dragon Tornado Riptide


33 41 35


110 38


The park boasts that the average height of their roller coasters is 50 metres. Explain how this is misleading.


3. In a certain company the wages earned are as follows: Employee 1 earned €8 000 Employee 2 earned €12 000 Employee 3 earned €8 000 Employee 4 earned €8 000 The director of the company earned €175 000


(i) Calculate the mean, mode and median of the wages. (ii) Is the mean a good reflection of the wages earned? Justify your answer. (iii) Which measure of central tendency would you choose to represent the average? Justify your answer.


4. Having collected data from her classmates about the sports they are involved in, Gabi drew the two graphs shown.


(i) Write two statements comparing these two graphs on first impressions.


(ii) What features of the graphs make it seem that the girls participate in sports more than the boys?


(iii) How could the graphs be changed to present the data more accurately?


Boys’ participation


25 35


30


15 20


10 5 0


12 16


10 14


8


6 4 2 0


Sport Sport Section A Applying our skills 139 Girls’ participation


7 Statistics 2


Number of participants


Number of participants


Swimming Football


Basketball


Cross-country running


Swimming Football


Basketball


Cross-country running


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