19 and 20 please 18) As the sample size increases, the margin of error a) increa

Question

19 and 20 please

18) As the sample size increases, the margin of error a) increases stays the same c)) decreases d) None of the other answers are correct. 19) A random sample of 100 observations has a mean of 20, a median of 21, and a mode of 22. The population standard deviation is known to equal 5 The 90% confidence interval for the population 15.2 to 24.8 19.2 to 20.8 19.216 to 20.784 19.178 to 20.822 20) A random sample of 36 statistics examinations was taken. The average score in the sample was I0 with a variance of 1 00. Assuming the scores are normally distributed, the OO% condence interval for the population average examination score is a) 5.021 to 14.981 14.540 X Z c) 5.062 to 15.968 5.482 to 15.521 X 8.2 (0.4) Section II: Short Answer Questions. (10 points each) 0a of the students are female. If a random sample of 10 students is selected,

Explanation / Answer

19

we are given that
n = 100
mean = 20
sd = 5

and the z value for 90% CI is 1.644 , from the z table

we know that the confidence interval is given as

mean +- z*sd/sqrt(n)

20 +- 1.644*5/sqrt(100), solving for the plus and the minus sign we get the interval as

19.178
and 20.822

Hence D

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