Descriptive Statistics
Ways of summarizing and organizing data sets and tests hypotheses
What is descriptive statistics?
Representation of a typical score in a distribution
What is central tendency?
The spread of scores in a distribution.
What is variability?
A graph of the means for different conditions in a study where the bar height represents the size of the mean.
What is a "bar graph"?
What does an inferential test provide?
What is "Test of the null hypotheses for either one-tailed or two-tailed hypotheses."
The difference between the observations in a population and in the sample that represents that population in a study.
What is "sampling error"?
Which value is not a measure of central tendency?
a. variance
b. median
c. mode
d. mean
What is "Variance"?
How can we find the range?
What is "the difference between the highest and lowest scores in a distribution"?
Which type of graph is appropriate for showing the nation of birth of all Hunter College students?
a. histogram
b. bar graph
c. frequency polygon
d. line graph
What is "b. bar graph"?
The ability of a significance test to detect an effect or relationship when one exists
What is "power"?
Indicate which of the following is a descriptive or inferential statistic:
a) A table of data (e.g. box scores; points, rebounds, etc from a basketball game)
b) The average of a data set (average snowfall in January in NYC)
c) A prediction based on the data (less snow is predicted this year)
d) A conclusion made about a population from a sample (battery life is longer on new iphones)
What is "a) descriptive, b) descriptive, c) inferential, d) inferential"?
What are the two factors we need to know about the data when choosing the correct measure of central tendency?
a. variance and scale of measurement
b. scale of measurement and the range of data
c. shape of the distribution and variance
d. shape of the distribution and scale of measurement
What is "shape of the distribution and scale of measurement"?
In a positively skewed curve ...
a. high scores are more frequent and the mean is larger than the median
b. low scores are more frequent and the mean is larger than the median
c. high scores are more frequent and the mean is smaller than the median
d. low scores are more frequent and the mean is smaller than the median
What is "b. low scores are more frequent and the mean is larger than the median"?
Where are the scores for a positive skew?
Where are the scores for a negative skew?
What is skewed left scores?
What is skewed right scores?
State the alternative and null hypothesis for this study:
Suppose you conducted a study to test the hypothesis that social pressure affects memory accuracy. You set up a study where participants view a video of a person robbing a convenience store. Then half of the participants watch a video of other “participants” discussing the crime. In reality, the “participants” in the video are part of the experiment, and some of the details of the crime that are discussed are inaccurate. The actual participants are told they should consider other people’s perspectives on the crime because it is difficult for any one person to accurately remember all the details. The other half of the participants do not view the video discussion of the crime but are also told that it is difficult for any one person to accurately remember all the details of the crime. Thirty min after viewing the original crime video, all participants are given a recognition memory test about details of the crime.
What is "Alternative Hypothesis: In the population, the video condition affects recognition scores, Null Hypothesis: In the population, the video condition does not affect recognition scores."
A __________ hypothesis is a directional hypothesis, whereas a ____________________ is no
What is "one-tailed, two-tailed"?
The value of the lowest score in a distribution is changed from X = 20 to X = 30. Which measure(s) of central tendency is (are) certain to be changed?
What is "mean"?
Why do we divide by n-1 for standard deviation?
What is "Because the scores are from a sample that represents the population, not from the population itself"?
For correlational studies, what variable is plotted on the X and the Y?
What is "X = predictor, Y - outcome"?
Suppose that the test statistic calculated for this study yields a p value of.18. What decision should be made with regard to the null hypothesis (assume α =.05)? What can the researcher conclude about the poker players’ abilities?
What is "p > a, so the null hypothesis must be retained. The researcher cannot conclude that the poker players can predict another player’s hand at better than chance accuracy."
Using the frequency table below, calculate the mean, median, and mode:
x n
10 2
4 6
6 1
8 3
5 3
What is "Mean = 5.9, Median = 5, Mode = 4"?
Calculate the mean, median and mode of the numbers listed below:
5 6 8 3 3 5 9 9 9
What is "Mean = 6.33, Median = 6, Mode = 6"?
Calculate the standard deviation of the numbers listed below:
7, 9, 8, 10, 11, 7, 8
What is "1.512"?
In a negatively skewed distribution of exam scores, Joann scored at the mean, Sara scored at the median, and Carl scored at the mode.
a. Who had the highest score?
b. Who had the lowest score?
c. Please draw the curve and note where each person's score would fall on it.
What is a) Carl, b) Joann
Donated blood is tested for infectious diseases and other contaminants. Since most donated blood is safe, workers save time and money by testing batches of donated blood rather than testing individual samples. Workers perform a test to check if a certain toxin is present, and the entire batch is discarded if the toxin is detected. This is similar to using a null and an alternative hypothesis to determine whether to discard the batch. The hypotheses being tested could be stated as:
H0: The batch does not contain the toxin.
HA: The batch contains the toxin.
Which of the following conditions would the testers commit a Type II error?
What is "The batch actually contains the toxin, and they conclude it does not."
Explanation: This is a Type II error—HA is true, but we fail to reject H0.