Year 9 Science · Unit 4 · Lesson 12
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Learning Goals
True or False? Fix the false ones
Circle T or F for each statement. If the statement is false, rewrite it correctly on the line below.
The mean is found by adding all the values and dividing by how many values there are.
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The median is the largest value in a dataset.
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A large outlier can pull the mean a long way from the typical value.
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To find a median you can use the values in any order.
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Scenario
A Year 9 student, Jordan, measures how many seconds 5 paper planes stayed in the air: 4, 6, 7, 7 and 11 seconds. Jordan wants to summarise the flights with descriptive statistics.
(a) Calculate the mean flight time. Show your working.
(b) Write down the median, the mode and the range of the flight times.
(c) Jordan now adds one more flight that stayed up for 40 seconds. Explain what this outlier does to the mean, and which average now better describes a typical flight.
1. A teacher records the marks of 9 students in a frequency table: a mark of 6 appears once, 7 appears twice, 8 appears three times, 9 appears twice, and 10 appears once. State the mode and calculate the mean. Show your working.
2. Give two benefits of using descriptive statistics instead of reporting every single value in a large dataset.
Wrap Up
In one sentence, what was the main idea of this lesson?