56.6k views
2 votes
Birth Weights: A simple random sample of 81 births of Chinese babies resulted in a mean birth weight of 3245 g and a standard deviation of 466 g. Test the claim that the standard deviation of birth weights of Chinese babies is equal to 567 g, which is the standard deviation of birth weights of Caucasian babies. Use a 0.01 significance level and assume that the birth weights are normally distributed.

User Kassem
by
7.2k points

1 Answer

0 votes

Final answer:

To test the claim that the standard deviation of birth weights of Chinese babies is equal to 567 g, the chi-square test for variability is used. The null hypothesis states that the population variance equals 567 squared grams squared, and it is tested against an alternative hypothesis with a significance level of 0.01.

Step-by-step explanation:

To test the claim that the standard deviation of birth weights of Chinese babies is equal to 567 g, we use the chi-square test for variability. With a sample of 81 Chinese babies with a mean birth weight of 3245 g and a standard deviation of 466 g, we want to test if there is a significant difference compared to the standard deviation of 567 g for Caucasian babies.

We will formulate the hypotheses as follows:

  • H0: σ^2 = 567^2 (The population variance is 567 squared grams squared.)
  • Ha: σ^2 ≠ 567^2 (The population variance is not 567 squared grams squared.)

The test statistic for this hypothesis test is calculated using the formula:

Chi-square statistic = (n - 1)s^2 / σ^2

where n = 81 (the sample size), s = 466 g (the sample standard deviation), and σ = 567 g (the claimed population standard deviation).

Plugging in the values, we get:

Chi-square statistic = (81 - 1) * 466^2 / 567^2

The calculated chi-square statistic is then compared against the chi-square distribution table value with n - 1 degrees of freedom (80 in this case), at the chosen significance level of 0.01 to determine if the null hypothesis can be rejected.

User Freonix
by
7.5k points