High School

3. The scatter diagram shows the
speaking test scores and the writing
test scores for 15 students.
Writing
test score
20-
× ×
×
15-
×

* *

10-
×
×
5-
x
×
15
20
Speaking test score
a) One student's writing test score was much better than their speaking test score.
Draw a ring around this point on the scatter diagram.
b) What type of correlation is shown on the scatter diagram?
c) Draw a line of best fit on the scatter diagram.
(1 mark)
(1 mark)
d) One student's scores were not recorded on the scatter diagram. His writing test score was
10.
(1 mark)
Use your line of best fit to estimate his speaking test score.

3 The scatter diagram shows thespeaking test scores and the writingtest scores for 15 students Writingtest score20 15 10 5 x 1520Speaking test scorea One

Answer :

1.The point (18, 20) is circled on the scatter diagram.

2. The scatter diagram shows a positive correlation.

3. The line of best fit connects points approximately like (5, 4) and (20, 19)

4. For a writing test score of 10, the estimated speaking test score is around 8 or 9.

a) To identify the student whose writing test score was much better than their speaking test score, we need to find the point where the writing score is significantly higher than the speaking score.

Looking at the given points:

- Most points show a general trend where the writing and speaking scores are somewhat close to each other.

- However, the point (18, 20) stands out because the writing score (20) is higher than the speaking score (18).

b) To determine the type of correlation, observe the general trend of the points on the scatter diagram:

- The points generally increase together, meaning that as the speaking test score increases, the writing test score also tends to increase.

c) The line of best fit (also known as the trend line) should be drawn to best represent the general direction of the data points on the scatter diagram. This line typically passes through the middle of the data points, balancing the number of points above and below it.

d) To estimate the missing speaking test score for the student whose writing test score was 10, find where the writing score of 10 would intersect the line of best fit.

If we use the approximate line of best fit from the previous step, we can estimate:

- For a writing test score of 10, the corresponding speaking test score from the line of best fit would be approximately around 8 or 9, based on the general trend.