Find Probability of 3 Samples from Chi-Square Distribution Exceeding 7.779

[Kites]

Homework Statement

If 15 Observations are taken independently from a chi-square distribution with 4 degrees of freedom, find the probability that at most 3 of the 15 sample items exceed 7.779

Homework Equations

The Attempt at a Solution

This problem should be quite simple. I find that in the back of my text that the chi square distribution of 7.779 is .9... but the answer is .9444... I am at a loss at why it is not exactly .9 and where to go from here. I would appreciate any help. Thanks.

 

[EnumaElish]

Have you taken into consideration that the problem asks for "at most 3"?