Microsoft Office Tutorials and References

In Depth Information

6.9 End-of-Chapter Practice Problems

1. Suppose that you wanted to study the relationship between the number of

growth rings and the age of a Ponderosa pine tree (Pinus ponderosa). Is there a

relationship between these two variables? Let’s assume that you can measure

the growth rings that correspond to the number of years the tree has been

growing.

You have decided to use the age of the trees (in years) as the predictor, X, and

the number of growth rings as the criterion, Y. To test your Excel skills, you have

randomly chosen eight trees, and have recorded the hypothetical scores on these

variables in Fig.
6.30
:

Fig. 6.30

Worksheet data for Chap. 6: practice problem #1

Create an Excel spreadsheet and enter the data using AGE as the independent

variable (predictor) and NUMBER OF GROWTH RINGS as the dependent

variable (criterion).

Important note: When you are trying to ﬁnd a correlation between two variables, it

is important that you place the predictor, X, ON THE LEFT

COLUMN in your Excel spreadsheet, and the criterion, Y,

IMMEDIATELY TO THE RIGHT OF THE X COLUMN. You

should do this every time that you want to use Excel to ﬁnd a

correlation between two variables to check your thinking so that

you do not confuse these two variables with one another.

(a) Create the table using Excel, and then use Excel’s = correl function to ﬁnd the

correlation between these two variables, and round off the result to two

decimal places. Label the correlation and place it beneath the table.

(b) Create an XY scatterplot of these two sets of data such that:

• Top

title:

RELATIONSHIP

BETWEEN

AGE

AND

NUMBER

OF

GROWTH RINGS IN PONDEROSA PINE TREES

• x-axis title: AGE (years)

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