A researcher acquires a set of 30 infant birthweights from a local hospital. The sample mean and variance are respectively 122.2 oz and 26.3 oz. A chi-squared goodness-of-fit test for normally distributed data uses the groups and frequencies in the table. The expected birthweight frequency for group 4 is: BW (oz) x< 102 Freq 6. 102 <= x < 122 10 122 <= x < 142 10 142 <= x 4 O 0.22 O none of these O 30.0 6.8 O 8.3 O O O
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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