Answer to Question #209335 in Statistics and Probability for Jhay

Question

Write the null hypothesis in words and in symbols.

1. A librarian of a school claims that all their Grade 9 students read an average of more than 10 books a month with a standard deviation of 2 books. A random sample of Grade 9 students read an average of 12 books a month with a standard deviation of 1 book.

3. A researcher thinks that if expectant mothers use vitamin pills, the birth weight of the babies will increase. The average birth weight of the population is 8.6 pounds.Write the null hypothesis in words and in symbols.

4. An engineer hypothesizes that the mean number of defects can be decreased in a manufacturing process of compact disks by using robots instead of humans for certain tasks. The mean number of defective disks per 1000 is 18.

Answer 1

1.

a.) The null hypothesis is a typical statistical theory which suggests that no statistical relationship and significance exists in a set of given single observed variable, between two sets of observed data and measured phenomena.

Null hypothesis: The average number of books that grade 9 students read in a month is no greater than10.

Alternative hypothesis: The average number of books that grade 9 students read in a month is greater than 10.

$H_0:\mu\leq10$

$H_1:\mu>10$

3.

A researcher thinks that if expectant mothers use vitamin pills, the birth weight of the babies will increase (>). The average birth weight of the population is 8.6 (=k) pounds. 

$H_0:\mu\leq8.6$

$H_1:\mu>8.6$

4.

An engineer hypothesizes that the mean number of defects can be decreased (<) in a manufacturing process of compact disks by using robots instead of humans for certain tasks. The mean number of defective disks per box is 18 (=k).

$H_0:\mu\geq18$

$H_1:\mu<18$