1. True or False. Justify for full credit. (a) If P(A) = 0.4, P(B) = 0.5, and A

Question

1. True or False. Justify for full credit. (a) If P(A) = 0.4, P(B) = 0.5, and A and B are disjoint, then P(A OR B) = 0.9. (b) If the variance of a data set is 0, then all the observations in this data set must be zero. (c) The mean is always equal to the median for a normal distribution. (d) A 95% confidence interval is wider than a 98% confidence interval of the same parameter. (e) In a left-tailed test, the value of the test statistic is -2. The test statistic follows a distribution with the distribution curve shown below. If we know the shaded area is 0.03, then we have sufficient evidence to reject the null hypothesis at 0.05 level of significance.

Explanation / Answer

a)true as for disjoint P(A or B) =P(A)+P(B) cause P(A and B)=0

b) false ; then all the observations in this data set must be equal

c) true ; being symmetric ; equal number of values and equal in magnitude are on both side of mean

d)

false ; cause for greater confidence level margin of error is greater

e) true ; cause if p value is less than level of significance we reject null

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