Question

Use this information for questions 7 - 11. A researcher desires to know if the age of a child is related to the number of cavities he or she has. Fill out at a minimum the sums of each of the columns, then answer the questions. (If you have a TI-84, try entering x into L1, y into L2, then do STAT -- CALC -- 2 Var Stats to get the sums.)

Age of child, x

6

8

9

10

12

14

Number of cavities, y

2

1

3

4

6

5

a. Draw a scatter plot and label the axes.

b. This shows a positive/negative linear relationship?

c. The dependent variable is age/peak heart rate?

8) Find the correlation coefficient. To show your work, at a minimum show me the formula with the numbers plugged in so I know what you keyed into your calculator.

9) Perform a 5 step traditional hypotheses test to see if there is a significant relationship between the age of a child and the number of cavities he or she has using ? = 0.05. Use either the CV/TV methods like they do in the examples (and in previous chapters) or use Table I - your choice.

10) Determine the regression line equation (there should be one.). To show your work, at a minimum show me the formula with the numbers plugged in so I know what you keyed into your calculator

11) Predict the number of cavities for children ages 7 and 13. Use these predictions to help graph the regression line on your scatter plot.

Answer 1

a) take x on the horizontal axis and y on the vertical axis. Plot the different combinations of x,y given to get the scatterplot. It will show a positive linear relationship.

b) Yes, the scatterplot shows a positive relationship because as x(age) increases, y(no. Of cavities) also increases.

c.) No. Of cavities is the dependent variable here.

11) Putting x=7 in the regression equation we get the value of y as, -1.918 + 0.551*7 = 1.939

Putting x=13, we get y= 5.245