stats
posted by Anonymous .
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)
Respond to this Question
Similar Questions

science
How bad are lice really for your health and can they cause any major diseases? 
English
I have to write my cure for an "ill" that plague teenagers. This one poem provides a good example of what I'm trying to do. I t is calles Scrawny's surfire ance cure. The plague in it was zits, and the cure it suggested was First apply … 
Math
The table shows the number of classrooms needed for different numbers of students. Total Students Classrooms 66 3 110 5 154 7 220 10 What is the relationship between Total Students and Classrooms? 
Grammar
Mother wondered from __________ her children had gotten the head lice. A) who B) whom I answered b 
Statics
17. The Student Health Service assumes, based on historical data, that the height of female students is normally distributed with a standard deviation of 3 inches. The school nurse wants to estimate the average height of this year’s … 
Math
School A has 480 students and 16 classrooms. School b has 192 students and 12 classrooms. A. what is the ratio of students to classrooms at School A? 
Math
School A has 480 students and 16 classrooms, School B has 192 students and 12 classrooms. How many students would have to transfer from School A to School B for the ratios of students to classrooms at both schools to be the same? 
Statistics
The results of a poll are stated as follows: “Based on a survey of 156 randomly selected students, 90% of the student body of 2870 students agree that no student should have to take final exams in two consecutive exam periods”. … 
Math
During a recent survey of two middle school classrooms, 1/3 of the students reported that they bring their lunch to school. Another 1/4 reported that they buy their lunch in the cafeteria and 1/6 reported going home for lunch. The … 
Math
In a random sample of 30 sixth graders, 9 had traveled outside of the United States. There are a total of 120 sixth graders in the school. Predict how many students have traveled outside of the United States. A 28 students B 36 students** …