DEFINITION of 'GoodnessOfFit'
Used in statistics and statistical modelling to compare an anticipated frequency to an actual frequency. Goodnessoffit tests are often used in business decision making. In order to calculate a chisquare goodnessoffit, it is necessary to first state the null hypothesis and the alternative hypothesis, choose a significance level (such as α = 0.5) and determine the critical value.
INVESTOPEDIA EXPLAINS 'GoodnessOfFit'
For example, a small community gym might be operating under the assumption that it has its highest attendance on Mondays, Tuesdays and Saturdays, average attendance on Wednesdays and Thursdays, and lowest attendance on Fridays and Sundays. Based on these assumptions, the gym employs a certain number of staff each day to check in members, clean facilities, offer training services and teach classes. However, the gym is not performing well financially and the owner wants to know if these attendance assumptions and staffing levels are correct. The owner decides to count the number of gym attendees each day for six weeks. He can then compare the gym's assumed attendance with its observed attendance using a chisquare goodnessoffit test for example. With the new data, he can determine how to best manage the gym and improve profitability.

Chi Square Statistic
A measurement of how expectations compare to results. The data ... 
Degrees Of Freedom
In statistics, the number of values in a study that are free ... 
Statistical Significance
A result that is not likely to occur randomly, but rather is ... 
Type I Error
A type of error that occurs when a null hypothesis is rejected ... 
Type II Error
A statistical term used within the context of hypothesis testing ... 
Probability Distribution
A statistical function that describes all the possible values ...

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