In: Statistics and Probability
When analyzing the last digits of telephone numbers in Sandtown, it was found that among 1500 randomly selected phone numbers, 225 had zero as the last digit. If the digits are selected randomly, the proportion of zeroes should be 0.1 because from probability, 0 is one of the 10 possible digits.
You may use StatCrunch or TI-83/84 calculator to do these calculations but be sure to include the printout in your post.
By using the TI-84 Calculator we have to solve this question.
Claim: The proportion of zeroes is not equal to 0.1
The null and alternative hypothesis is
H0: P = 0.1
H1: P 0.1
Level of significance = 0.01
Sample size = n = 1500
x = 225
The TI-84 calculator path is Click on STAT --------->TESTS -------->1-PropZTest------->
P0: 0.1
x: 225
n: 1500
prop: p0
Calculate
We get
z = 6.46
P-value = 0.0000
P-value < 0.01 we reject null hypothesis.
Conclusion:
The proportion of zeroes is not equal to 0.1
Now we have to construct a 99% confidence interval to estimate the proportion of zeroes.
TI-84 Calculator path is Click on STAT --------> TESTS ---------> 1-PropZInt --------->
x: 225
n: 1500
C-Level: 0.99
Calculate
We get
So the confidence interval is (0.1263, 0.1738)
The value 0.1 does not belong to the above interval so we reject the null hypothesis.
Both results are the same.