Thursday
October 23, 2014

Homework Help: stats

Posted by Anonymous on Friday, June 1, 2007 at 1:40pm.

Head lice can be a problem in classrooms. From the past experience, suppose it is predicted that 5% of the students will get lice if there are some reported cases. The health nurse checks 120 randomly chosen students and records the number of students that have head lice. What is the probability that exactly 6, 7, 8 students in the random sample have head ice?

How would I do this question??

I presume you mean that there is a 5% chance that a student, drawn at random, will have lice.

You could solve this exactly as a combinatorial problem. The probability of seeing exactly 6 is:
(.95^114 * .05^6)*Z, where Z is 120!/(6!*114!) (where ! means factorial). Repeat for exactly 7 and exactly 8.

Or you could solve approximately and use the properties of a binominal distribution. Here, the expected mean is .05*120=6, the standard deviation is sqrt(120*.05*95)=2.37 So, 8 is .84 standard deviations away from the mean. Use a cumulative normal distribution table to find your probability. (But, I wouldnt use 8, I would use 8.5)

Answer this Question

First Name:
School Subject:
Answer:

Related Questions

Math - The table shows the number of classrooms needed for different numbers of ...
Grammar - Mother wondered from __________ her children had gotten the head lice...
English - I have to write my cure for an "ill" that plague teenagers. This one ...
childcare - 14. Caregivers shouldn't allow dress-up play with hats when _______ ...
math - (Mad +lice)+(equations + r +p - square)= decimal_______
science - How bad are lice really for your health and can they cause any major ...
math - (Math+lice)+ (equations+R+P- Square)= Decimal_______ I don't have a clue ...
Sexually Transmitted Infections - What are the temporary and longterm effects of...
Ms.Sue - Yesterday I wasn't able to post so I here I am posting it today for you...
unscramble grammar - I need help descrambling 2 sentences: 1 - insects plant eat...

Search
Members