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Which of the following are correct?

(A) A statistical hypothesis is a statement about the population parameter which may be true or false.

(B) In a statistical hypothesis testing procedure, a Type I error is made when the null hypothesis is accepted when it is false.

(C) In a statistical hypothesis testing procedure, a Type II error is made when the null hypothesis is rejected when it is true.

(D) The number of degrees of freedom of a statistic is the number of independent variates used to compute that statistic.

Choose the correct answer from the options given below:

Solution

Correct Option: 2

Statement (A): A statistical hypothesis is a statement about the population parameter which may be true or false.

This statement is correct. A hypothesis is a claim about a population parameter (like average height, proportion of voters, etc.) that can either be true or false until tested.


Statement (B): In a statistical hypothesis testing procedure, a Type I error is made when the null hypothesis is accepted when it is false.

This statement is incorrect.

Type I Error occurs when the null hypothesis is rejected when it is actually true (false alarm).

Type II Error occurs when the null hypothesis is accepted when it is actually false (missed detection).

Statement B describes Type II error, not Type I error.


Statement (C): In a statistical hypothesis testing procedure, a Type II error is made when the null hypothesis is rejected when it is true.

This statement is incorrect.

Statement C describes Type I error, not Type II error. The definitions are reversed.


Statement (D): The number of degrees of freedom of a statistic is the number of independent variates used to compute that statistic.

This statement is correct. Degrees of freedom (df) represents the number of independent pieces of information available to compute a statistic.

For example, if there are 10 numbers with a known average, only 9 are free to vary (the 10th is fixed), so df =n1=9= n - 1 = 9.


Only statements (A) and (D) are correct.

Therefore, the answer is Option 2.

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