Example 9: Cell Phone Calls A survey of 1,917 cell phone users in May 2010 asked “On an average day, about how many cell phone calls do you make and receive on your cell phone?” The mean number of calls was 13.10, with a standard deviation of about 10.2. Find and interpret a 99% confidence interval for the mean number of cell phone calls for all cell phone users. Use t* = 2.578
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.
Example 9: Cell Phone Calls
A survey of 1,917 cell phone users in May 2010 asked “On an average day, about how many cell phone calls do you make and receive on your cell phone?” The mean number of calls was 13.10, with a standard deviation of about 10.2. Find and interpret a 99% confidence interval for the mean number of cell phone calls for all cell phone users. Use t* = 2.578
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