exam 1 practice q's
A set of n = 6 scores has a mean of M = 10. Another set of scores has n = 4 and M = 15. If these two sets of scores are combined, what is the weighted mean for the combined group?
12 6 x 10 = 60 4 x 15 = 60 120/(6+4) = 12
For a sample of n = 16 scores, how many scores are used to calculate the sample variance?
16
What is the value of Σ(X + 1) for the following scores? Scores: 2, 4, 7
16
What is the value of SS for the following set of sample scores? Scores: 0, 1, 4, 5
17
On an exam with μ = 52, you have a score of X = 56. Which of the following values for the standard deviation would give you the highest position in the class distribution?
2 smallest possible deviation
A sample from a population with μ = 40 and σ = 10 has a mean of M = 44. If the sample mean corresponds to a z = 2.00, then how many scores are in the sample?
25
A population has sum of squared deviations, SS = 100 and variance, s^2 = 4. How many scores are in the population?
25 ss/s^2
A sample of n = 25 scores has mean M = 20 and variance s^2= 9. What is the sample standard deviation?
3 sqrt s^2
The sum of the squared deviation scores is SS = 20 for a sample of n = 5 scores. What is the variance for this sample?
4 ss/n
A sample of n = 8 scores has SS = 50. If these same scores were a population, then the SS value for the population would be ____.
50
Samples of size n = 9 are selected from a population with μ = 80 with σ = 18. What is the standard error for the distribution of sample means?
6
Samples of size n = 9 are selected from a population with μ = 80 with σ = 18. What is the expected value of M, the mean of the distribution of sample means?
80
Under what circumstances is a score that is 15 points above the mean an extreme score relatively far from the mean?
When the population standard deviation is much smaller than 15
Using z-scores, a population with μ = 37 and s = 6 is standardized so that the new mean is μ = 50 and s = 10. After the standardization, one individual has a score of X = 55. What was this individual's score in the original distribution?
X = 40
As the sample size increases, the standard error also increases.
false
For the following scores, ΣX = 49. Scores: 1, 4, 2, 0
false
The mean for a sample of n = 4 scores has a standard error σ = 5 points. This sample was selected from a population with a standard deviation of σ = 20.
false
A distribution is positively skewed. Which is the most probable order, from smallest to largest, for the three measures of central tendency?
mode, median, mean
What frequency distribution graph is appropriate for scores measured on a nominal scale?
only a bar graph
Determining the class standing (1 , 2 , and so on) for the graduating seniors at a high school would involve measurement on a(n) ____ scale of measurement.
ordinal
Determining a person's reaction time (in milliseconds) would involve measurement on a(n) ____ scale of measurement.
ratio
A researcher is interested in the eating behavior of rats and selects a group of 25 rats to be tested in a research study. The group of 25 rats is an example of a ____.
sample
If sample variance is computed by dividing SS by df = n - 1, then the average value of the sample variances from all the possible random samples will be ____ the population variance.
smaller than
For the following scores, ΣX = 35. Scores: 1, 3, 5
true
Recording the number of students who are absent each day at a high school would be an example of measuring a discrete variable.
true
The process of transforming every x value in a distribution into a corresponding z-score to create a distribution of z-scores is called a z-score transformation.
true
The range and the standard deviation are both measures of spread.
true
In a correlational study, ____.
two variables are measured and two groups are compared
A sample of n = 20 scores has a mean of M = 45 and a standard deviation of s = 8. In this sample, what is the z-score corresponding to X = 57?
z = 1.50
A population of scores has μ = 50 and σ = 5. If every score in the population is multiplied by 3, then what are the new values for the mean and standard deviation?
μ = 150 and σ = 15 both mean and stdev are multiplied
You have a score of X = 75 on a statistics exam. The mean score for the class on the exam is μ = 70. Which of the following values for the standard deviation would give you the highest position within the class?
σ = 1 "In this case, your score is 75 and the mean is 70. A SD of 5 would mean that you are just part of the 70% middle pack and there is nothing special about you. A SD of 1 means that you are five SDs above the mean, which makes you the top 1% of the population and you are indeed very special. Therefore, you would want the SD to be as small as possible in this case."
What happens to the expected value of M as sample size increases?
It stays constant.
If the score is lower than the mean, you would want
a standard deviation that is as large as possible to get a better position.
What position in the distribution corresponds to a z-score of z = +2.00?
Above the mean by a distance equal to 2 standard deviations
Which description provides an example of a discrete variable?
The gender of each student in a psychology class
Statistical methods that organize, summarize, or streamline data are called ____.
descriptive statistics
A set of scores ranges from X = 18 to X= 91. If the scores are put in a grouped frequency distribution table with an interval width of 10 points, the top interval would be 91-100.
false