Problem 3, page 455. Checkout time at a supermarket is monitored using a mean and range chart. Six samples of n=20 observation have been obtained and the sample means and ranges computed: Sample Mean Range Sample Mean Range 1 3.06 0.42 4 3.13 0.46 3.15 0.5 3.06 0.46 3 3.11 0.41 6. 3.09 0.45 a. Using the factors in the table, determine UCL and LCL for mean & range chart. b. Is the process under control?
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.
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