Hi there,
H0: no difference between the entrances
Ha: difference between the entrances
Using a table (http://www.itl.nist.gov/div898/handbook/eda/section3/eda3674.htm), the critical value is (df = N-1 = 3, alpha = 0.01):
11.345
So we reject the null for values greater than that.
The expected value for each entrance is 100, so get chi squared:
(140-100)^2/100 + (120-100)^2/100 + (90-100)^2/100 + (50-100)^2/100
= 46
The chi squared value is much higher than the critical value, so we reject the null hypothesis and conclude that there is a difference between the entrances.
Let me know if you have any questions, and please don't forget to accept all these answers.
-Scott
MIT Graduate
College degree in math... proficient in all levels -- from algebra to calculus