Psy Midterm 2
About ______ of z-scores in the standard normal distribution are between the z-scores ±1.96.
95%
For a variable that is normally distributed with a mean of 150 and a standard deviation of 25, approximately ______ of the scores are between ______ and ______.
95%; 100 and 200
______ separates the regions of rejection and non-rejection.
A critical value
α refers to ______.
the probability of a statistic needed to reject the null hypothesis
The interquartile range can be defined as ______.
the range of the middle 50% of the scores in a set of data
After grading an examination, an instructor realizes there is a wide range of ability in her class. He realizes this because ______ than she expected.
the standard deviation was higher
After grading an exam, an instructor realizes there is a very narrow range of ability in her class. He realizes this because ______ than she expected.
the standard deviation was smaller
Normal distributions are an important concept to researchers because ______.
they are the basis of statistical techniques designed to test hypotheses
In this figure, if the value of a calculated statistic falls in the ______ , you will ______.
unshaded area; not reject the null hypothesis
The average squared deviation of a score from the mean is the ______.
variance
You can apply the normal curve table to a standardized distribution ______.
when the distribution of raw scores is normally distributed
You would calculate parameters rather than statistics for a set of data you have collected when ______.
you have collected data from the entire population
IQ scores based on the Wechsler Adult Intelligence Scale are assumed to be normally distributed with a mean of 100 and a standard deviation of 15. What is the z-score for an IQ of 90?
z = -.67
A variable is normally distributed with a hypothesized population mean of 53 and a standard deviation of 9. What is the z-score for a raw score (X) of 46?
z = -.78
If a variable is normally distributed with a hypothesized mean (μ) of 32 and a standard deviation (σ) of 5, what is the z-score for a raw score (X) of 41?
z = 1.80
The statement ______ is an example of a ______
μ = 5; null hypothesis
______ is an example of a ______.
μ; parameter
______ is an example of a ______.
σ; measure of variability
A statistical hypothesis that contains the ______ symbol may be defined as ______.
≠; two-tailed
What is the population standard deviation for this set of data? 7, 9, 5, 12
2.59
What is the interquartile range for this set of data? 5, 4, 7, 2, 9, 1, 11, 8
4
What is the standard deviation for this set of sample data? 2, 6, 10
4.00
What is the standard deviation for this set of sample data? 24, 18, 21, 28
4.27
What percentage of z-scores in the standard normal distribution are less than z = .20?
57.93%
What is the range for this set of data? 11, 6, 5, 7, 13, 12
8
What z-score designates or marks the bottom 20% of the standard normal distribution?
-.84
In the standard normal distribution, the mean is equal to ______ and the standard deviation is equal to ______.
0; 1
Imagine the average score on this exam ends up being 71 with a standard deviation of 10. If scores are normally distributed, ______ is the lowest score that would place you in the top 20% of the class.
80
What is the population standard deviation for this set of data? 72, 61, 80, 76, 54
9.67
What is the variance for this set of sample data? 6, 7, 10, 13
10.00
For this set of sample data, the standard deviation is equal to ______. 104, 116, 95, 121, 87
14.15
"Imagine you are president of a toy company that builds video games. You have determined that the time needed to build these games is normally distributed with a mean of 20 minutes and a standard deviation of 5 minutes." What percentage of video games are built in LESS than 15 minutes?
15.87%
Which of the following beliefs is the BEST example of a null hypothesis, H0?
American Olympic skiers are not better than the rest of the world.
Which of the following beliefs is the BEST example of an alternative hypothesis, H1?
I am more likely to buy a product if it is endorsed by my favorite actor.
Imagine this figure is designed to represent a normal distribution. What is one problem with it?
It does not contain an infinite number of scores.
Compared with other measures of variability, what is a strength of the range?
It is quick and easy to compute.
The ______ the sample size, the ______ likely you are to reject the null hypothesis.
larger; more
"Your score on this variable is about one-half of a standard deviation below the mean." Which of the following statements is MOST accurate?
Your z-score is -.53.
"Your score is about three-fourths of a standard deviation above the mean." Which of the following statements is most accurate?
Your z-score is .71.
Roughly ______ of z-scores in the standard normal distribution are within ±3 standard deviations of the mean.
all
A binomial distribution is used for a variable ______.
consisting of exactly two categories
George calculates a standard deviation and obtains a value of s = -5.37. This necessarily implies ______.
he has calculated wrong
The shaded area in this distribution most closely represents ______.
the % of z-scores between -.80 and 2.00
The addition rule of probability relates to ______.
the combined probabilities of mutually exclusive outcomes
Mathematically, probability may be defined as ______.
the number of ways an outcome may occur divided by the total number of possible outcomes
If a negatively skewed frequency distribution of raw scores is converted into z-scores, the shape of the new distribution will be ______.
negatively skewed
One difference between normal distributions and frequency distributions is that ______.
normal distributions are hypothetical; frequency distributions are based on actual data
You will make the decision to ______ the null hypothesis when the probability of the statistic is ______.
not reject; high
The ______ hypothesis states that there is no difference or relationship among groups and the ______ hypothesis states that there is a difference or relationship among groups.
null; alternative
Which of these is not based on all of the scores in a set of data?
range
The ______ primarily measures the ______ of a distribution of scores for a variable.
range; variability
If the calculated statistic falls in the ______, you will ______.
region of rejection; reject the null hypothesis
If you were to draw 15 random samples of 100 residents in a city you may get 15 different means. These differences across samples may be defined as ______.
sampling error
The concept of ______ refers to differences between statistics calculated from a sample and statistics pertaining to the population from which the sample is drawn.
sampling error
A decision rule ______.
specifies the values of a statistic that lead to rejection of the null hypothesis
The ______ measures the ______ of a distribution of scores for a variable.
standard deviation; variability
The ______ of a normal distribution is equal to ______.
standard deviation; σ
Which of the following is the first step in hypothesis testing?
state the null and alternative hypothesis
When the decision to reject the null hypothesis is made, ______.
support has been provided for the research hypothesis
An event may be defined as an action that ______.
takes place
