Question

1. A C level confidence interval is described as what? (3 points) Oan interval computed from a data sample by a method that has the probability C of producing an interval containing the true value of the parameter any interval within the margin of error O an interval with a margin of error C that is also correct C% of the time Oany interval that follows the 68-95-99.7 rules Oan interval computed from a data sample that guarantees that the probability the interval computed contains the parameter C of nterest 2. A sample of 25 seniors from a large urban school district has a mean Verbal SAT score of 450. (3 points) Assume you know that the standard deviation of the population of Verbal SAT scores for seniors in the district is s-100, A 90% confidence interval for the mean score μ for the population of seniors is used. Which of the following will produce a confidence interval with a smaller margin of error? O Using a confidence interval of 95% OUsing a sample of 100 0 Using an upper critical value of 99% OUsing a sample of 15 seniors OUsing any sample size smaller than 25 3. A sample of 100 janitors in a certain school district found that the average time each janitor (3 points) had worked for the school district was 8 years. Suppose you know that the standard deviation of the population is s 5 years. Construct a 95% confidence interval for the mean time of the population of janitors have spent with the school district 08士1 .98 08 ± 0.82 08 ±0.71 O8 1.53 O8+0.98

Answer 1

1)
option A)

2)
option B) sample of 100

as sample size increases, margin of error decreases

3)
mean = 8
margin of error = z *sd/sqrt(n)
= 1.96* 5/sqrt(100)
= 0.98

hence
option E) 8 +-0.98 is correct

4)
n= ( z *sd/e)^2
= (1.96 * 100/25)^2
= 61.46
=62

option D)

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