question archive In constructing a 95% confidence level estimate of the mean when the population standard deviation (σ) is known what will be your z score used in the formula? 2
In constructing a 95% confidence level estimate of the mean when the population standard deviation (σ) is known what will be your z score used in the formula? 2
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In constructing a 95% confidence level estimate of the mean
when the population standard deviation (σ) is known what will be your z score used in the formula?
2.) In constructing a 99% confidence level estimate of the mean when the population standard deviation (σ) is known what will be your z score used in the formula? HINT: Be sure to review page 236 "Finding Z scores from Known Areas - Special Cases" and Tabel A-2.
3.) In constructing a 90% confidence level estimate of the mean when the population standard deviation (σ) is known what will be your z score used in the formula? HINT: Be sure to review page 236 "Finding Z scores from Known Areas - Special Cases" and Tabel A-2.
If you identified it as 1.64 contact me in the DB and I will provide partial credit. Please see my lecture "CIE of the mean z and t examples 2015" as to an explanation as to why the correct answer is 1.645.
The Z value is a function of the level of confidence. The level of confidence is determined by whoever is performing the analysis and is often 90%, 95%, or 99%. Once the level of confidence is selected the "Z value" can be found. To find the Z value you divide the level of confidence by 2 and use the normal curve table.
For instance if the level of confidence is 95%, you divide .95 by 2 and get .4750 (for our purposes carry the number out to four places because our normal curve table goes out four places). Using the normal curve table you find .4750 in the "areas under the normal curve" section of the table, i.e. the 'heart' of the table. Once you find that number on/in the table you read across to the first column (the Z column) simultaneously reading to the top row (the z row), and select the number in the z column (1.9) and the number in the z row (0.06) combining the two thus getting the Z value of 1.96.
The Z value corresponding to a level of confidence of 90% is 1.645. Note .90/2 = .4500. In the areas under the normal curve table you see .4495 and .4501, but not .4500. The Z value for .4495 is 1.64. The Z value for .4501 is 1.65. Because .4500 is half way between .4495 and .4501 we use the half-way point between their corresponding Z values of 1.64 and 1.65 which is 1.645.
4.) In constructing a 98% confidence level estimate of the mean when the population standard deviation (σ) is known what will be your z score used in the formula?______
5.) In constructing a 95% confidence level estimate of the mean when the population standard deviation (σ) is unknown and the sample size is 40, what will be your t score used in the formula?________
6.) In constructing a 99% confidence level estimate of the mean when the population standard deviation (σ) is unknown and the sample size is 35, what will be your t score used in the formula?______
7.) In constructing a 90% confidence level estimate of the mean when the population standard deviation (σ) is unknown and the sample size is 30, what will be your t score used in the formula?_________
8.) In constructing a 98% confidence level estimate of the mean when the population standard deviation (σ) is unknown and the sample size is 33, what will be your t score used in the formula?_______
9.) Determine the upper limit of a 95% confidence level estimate of the mean when the population standard deviation (σ) is unknown and the sample size is 40, the sample mean is 110.27 and the sample standard deviation is 18.95._______
10.) Determine the upper limit of a 95% confidence level estimate of the population proportion when the sample size is 200 customers, 35 of whom respond yes to a survey.______
11.) In constructing a confidence interval estimate of the population mean you decide to select 49 random observations to get your point estimate of the mean (sample mean). Your friend is also constructing a similar confidence interval estimate but decides to use a sample size of 36 random observations. Which of the following is true?
a.Your confidence interval estimate has a greater degree of confidence.
b.Your confidence interval estimate is narrower.
c.Your confidence interval estimate is wider.
d.Your friend's confidence interval estimate has a greater degree of confidence.
12.) The width of a confidence interval estimate for a proportion will be:
a. Narrower when the sample proportion is .50 than when the sample proportion is .20
b.Narrower for 99% confidence level than for a 95% confidence level
c.Wider for a sample size of 100 than for a sample size of 75
d.Narrower for 90% confidence level than for a 95% confidence level
13.) The value of "Z" chosen for constructing (calculating) the confidence interval estimate is determined by
a.The sample size
b.The standard deviation
c.Correction factor
d.Level of confidence
14.) The value of "t" chosen for constructing (calculating) the confidence interval estimate is determined by
a. The standard deviation
b. The sample size
c. The level of confidence
d. The Level of confidence and the sample size
15.) A 99% confidence interval estimate of the population mean can be interpreted to mean that we have 99% confidence that the true population mean will fall within the confidence interval estimate.
True
False
16.) The sample mean and the sample standard deviation will vary from sample to sample
True
False
17.) The confidence interval estimate of the population mean is constructed around the sample mean (i.e. we add and subtract some amount to the mean).
True
False
18.) The confidence interval estimate of the population mean will be wider for a 95% confidence level than for a 90% confidence level. (assumes the sample size and sample standard remain constant)
True
False
19.) With respect to sampling methods the difference between a sample statistic and its corresponding population parameter is called the sampling error. True or false?
True
False
20.) The confidence interval estimate of the population mean will be _______ for a 95% confidence level than for a 90% confidence level. (Assuming the sample size and the standard deviation are constant)
A. narrower
B. wider
C. the same
D. indeterminant
