13.1 64.2 What is the correlation coefficient for this data set? To find the p-value for a correlation coefficient, you n
Inverse Normal Distribution
The method used for finding the corresponding z-critical value in a normal distribution using the known probability is said to be an inverse normal distribution. The inverse normal distribution is a continuous probability distribution with a family of two parameters.
Mean, Median, Mode
It is a descriptive summary of a data set. It can be defined by using some of the measures. The central tendencies do not provide information regarding individual data from the dataset. However, they give a summary of the data set. The central tendency or measure of central tendency is a central or typical value for a probability distribution.
Z-Scores
A z-score is a unit of measurement used in statistics to describe the position of a raw score in terms of its distance from the mean, measured with reference to standard deviation from the mean. Z-scores are useful in statistics because they allow comparison between two scores that belong to different normal distributions.
The data for two variables x and y is given in the following table,
x | y |
28.9 | 69.7 |
60.2 | 56.1 |
56.8 | 84.8 |
38.8 | 98.9 |
27.7 | 78.3 |
48.9 | 61.5 |
54.5 | 71.7 |
50.1 | 75.2 |
34.4 | 93.2 |
13.1 | 64.2 |
It is required to test the significance of correlation.
The given level of significance is 0.005.
First calculating the correlation coefficient
It can be calculated using MS-Excel.
Steps for calculating using MS-Excel are as follows
- Enter the data in MS-Excel
- Click on the Data toolbar >> Select the Data Analysis >>Correlation.
- Select the entire data as an input range. (Check labels if included)
The output will be
From the above output the correlation coefficient (r) = -0.11107
Rounding to three decimal
r = -0.111
The null and alternative hypothesis is
H0 : = 0
H1 :
Where is the population correlation coefficient.
The formula for test statistic is
= 0.3309673
Rounding to three decimal
t =0.331
The degree of freedom for the test is df = n -2 = 8
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