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f08_1 - Statistics 324(Bates Midterm 1(p 1 Choose the most...

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Statistics 324 (Bates) Midterm 1 2008-10-09 (p. 1) Choose the most appropriate answer. Mark only one selection. Use pencil. 1. In a single sample of data the 50th percentile is also called the sample (a) mean (b) median (c) range (d) standard deviation (e) variance 2. The formula for the sample standard deviation, s , is (a) p ( n i =1 x i ) /n (b) p ( n i =1 ( x i - ¯ x ) 2 ) /n (c) p ( n i =1 ( x i - ¯ x ) 2 ) / ( n - 1) (d) (∑ n i =1 ( x i - ¯ x ) 2 ) /n (e) (∑ n i =1 ( x i - ¯ x ) 2 ) / ( n - 1). 3. If s is the sample standard deviation and ¯ x is the sample mean we expect about 95% of the data to fall in the interval (a) s ± ¯ x (b) s ± x (c) ¯ x ± s (d) ¯ x ± 2 s (e) ¯ x ± 3 s 4. The box in a box-and-whisker plot covers what portion of the data? (a) 50% (b) 2/3 (c) 95% (d) 99% (e) no speciﬁc proportion - it will vary. 5. For a continuous random variable X , which statement is not always true of the probability density function, f ( x )? (a) 0 f ( x ) (b) f ( x ) 1 (c) R -∞ f ( x ) dx = 1 (d) P [ a X b ] = R b a f ( x ) dx (e) P [ a X < b ] = R b a f ( x ) dx 6. Which distribution is most commonly used to model the time to failure of a system? (a) bi- nomial (b) Poisson (c) normal (or Gaussian) (d) uniform (e) exponential 7. Which distribution is a continuous distribution? (a) binomial (b) geometric (c) hypergeomet- ric (d) negative binomial (e) normal (or Gaussian) 8. A binomial random variable, X , models the total number of successes in n independent, identical trials, each with probability

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f08_1 - Statistics 324(Bates Midterm 1(p 1 Choose the most...

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