Betty recorded the number of visitors at her art gallery during the week: Day Visitor
Tuesday 28
Wednesday 20
Thursday 18
Friday 14
She expected to have 20 visitors each day. To determine whether the number of visitors follows a uniform distribution, a chi-square test for goodness of fit should be performed (alpha = 0.10).
X^2 = Σ(O - E^2)/E
Using the data above, what is the chi-square test statistic?