Statistics in the eighth grade (4th grade) must always be well mastered. Thus, we will study in this lesson, the notion of average, the median of a statistical series and the range. In addition, the student should be able to draw a bar graph, a pie chart and a histogram, and also calculate frequencies. At the end of the chapter, the student will develop new skills and progress in math.
I. Range and median of a statistical series
Each 4th grader indicated the number of books they read in September.
Here are the results of the survey:
The study population is made up of students in grade 4B.
The character studied is the number of books read in September: it is a quantitative character.
Thetotal number of students is 25.
The difference between the largest and smallest values of the character is called the range of a statistical series.
10 – 0 = 10, so the range of the previous statistical series is 10 pounds.
To calculate the median of a statistical series, we can use a table of cumulative increasing numbers.
The first two rows of the table below are the population table for the series.
Since the total number of people is 25, the median value is the 13th value of the series when we arrange them in ascending order.
The median of this series is 2 because 2 is the smallest value in the series when arranged in ascending order.
II. The weighted average
To calculate the weighted average of a statistical series :
we calculate the sum of the products of the numbers by the value of the character then we divide by the total number of people.
We can calculate the average number of books read in 4°B in September.
On average, 4th graders read 2.36 books in the month of September.
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