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STATS
Final
| Question | Answer |
|---|---|
| T or F: When finding probabilities that deal with the sample mean, we may use the Central Limit Theorem as long as n > 30. | True |
| T or F; The central limit theorem states that, if n > 30, then the distribution of the sample means has the same mean and standard deviation as the population | False |
| Mean = 70 and SD = 5. A sample of 49 scores are taken from this population. What is the appropriate TI84 command for "the 1st quartile of the sample mean" | invNorm (0.25, 70, 5/7) |
| Mean = 70 and SD = 5. A sample of 49 scores are taken from this population. What is the appropriate TI84 command for "probability that the sample mean score is between 60 & 80) | normalcdf (60,80,70,5/7) |
| Mean = 70 and SD = 5. A sample of 49 scores are taken from this population. What is the appropriate TI84 command for "the 25th percentile for all test scores" | invNorm (.25, 70, 5) |
| Mean = 70 and SD = 5. A sample of 49 scores are taken from this population. What is the appropriate TI84 command for "probability that randomly selected INDIVIDUAL test score from the pop. is between 60 and 80" | normalcdf (60, 80, 70, 5) |
| If you are asked to find "the mean of the distribution of sample means" and the mean is 17 and n > 30 , according to the central limit therom, what is the mean of the distribution of sample means? | 17 b/c n > 30 |
| What should you do if asked to find the standard deviation of the distribution of the sample means? | Check if n > 30. If so, use this formula: standard deviation / square root of n |
| What command on TI 84 do you use when you're asked to find the probability that the average is less than, more than, or in between 2 numbers? | 1. complete formula: SD/ sq root of n 2. normal cdf (lower bound, upper bound, mean, SD from formula) |
| What command on TI 84 do you use when you're asked to find the ""th percentile for the sample mean? | 1. complete formula: SD/ sq root of n 2. invNorm (percentile, mean, SD from formula) |
| T or F: To use the central limit theorem for proportions, the quantities np and n(1 - p) must be greater than or equal to 10. | True |
| What should you do if asked to find the value of the mean of the distribution of sample proportions? | 1. Check that np and n (1 - p) is greater than or equal to 30 2. If so, the answer is p |
| What should you do if asked to find the value of the standard deviation of the distribution of sample proportions? | 1. Check that np and n (1 - p ) is greater than or equal to 30 2. If so, complete formula: square root of p (1 - p ) / n |
| What command on TI 84 do you use when you're asked to "find the mean or SD of the distribution of sample proportions? | normalcdf (if computing SD, compute this first: square root of p ( 1 - p ) / n |
| If we increase the confidence level and keep the same sample size, we _____ the margin of error | increase |
| If we want to increase our confidence that an interval contains the true value, we must ___ the critical value | increase |
| This ____ the margin of error, which makes the confidence interval | increases; wider |
| Will increasing sample size while keeping confidence level the same result in a narrower or wider confidence interval? | narrower |
| T or F: To construct a confidence interval for a population mean, we add and subtract the critical value from the point estimate | false |
| T or F: The margin of error is the product of the standard error and the critical value | true |
| T or F: The confidence level is the proportion of all possible samples for which the confidence interval will cover the true value | true |
| What is the critical value for 90%? | 1.645 |
| What is the critical value for 95%? | 1.96 |
| What is the critical value for 98%? | 2.326 |
| What is the critical value for 99%? | 2.576 |
| When you know the population standard deviation, how do you find upper and lower bounds? | Use z interval |
| T or F: The student's t curve is more spread out than the normal curve | true |
| T or F: The student's t distribution can be used to find a confidence interval for the population mean if outliers are present in a small sample | false |
| T or F: The assumptions for construction a confidence interval for the population SD is unknown are 1) simple random sample 2)either the sample is large or is approximately normal | True |
| T or F: When the number of degrees of freedom is small, the student's t distrbution is close to the normal distribution | False |
| When do we use z interval? | when we know population sd |
| when do we use t interval? | when we know sample sd |
| The ___ command on the TI 84 will compute the confidence interval for the mean when the population SD is not known | T interval |
| To construct a confidence interval for a population proportion, we use the ___ command on the calculator | 1-PropZInt |
| T or F: The margin of error does not depend on sample size | false |
| T or F: If the null hypothesis is rejected, we conclude that H1 is true | True |
| T or F: If the null hypothesis is not rejected we conclude that Ho is true | False |
| What type of error?: Rejecting Ho when it is true (rejecting null hypothesis when it's true) | type I error |
| What type of error: Rejecting Ho when it is false (rejecting null hypothesis when it's true) | correct decision |
| What type of error?: Failing to reject Ho when it is false (failing to reject null hypothesis when it's false) | type II error |
| What type of error?: Failing to reject Ho when it is true (failing to reject null hypothesis when it is true) | correct decision |
| T or F: The smaller the P-value, the stronger the evidence against Ho | True |
| T or F: If the P value is more than the significance level, we reject Ho | False |
| A ___ command in the calculator will perform a hypothesis test when the population SD is known ("use the TI 84 to compute the p value) | Z test |
| A ____ command in the calculator will perform a hypothesis test when the POPULATION SD is not known | T test |
| The correlation coefficient measures only the strength of the ___ relationship between two variables | linear |
| All points lie exactly on a straight line = the correlation coefficient r equals ___ | 1 |
| Larger values of one variable correspond to smaller values of the other variable = the correlation coefficient r is ___ | negative |
| Larger values of one variable correspond to larger values of the other variable = the correlation coefficient r is ___ | positive |
| The linear association between the variables is weak = the correlation coefficient r is close to ___ | 0 |
Created by:
jjohns53grad2