Chapter 1
What is the difference between a sample and a population?
Population represents all members of a certain group or category of interest. Sample is a subset drawn from a larger population
What does central tendency tell us about a sample?
what is typical of a sample
How do you calculate the interquartile range?
IQR = 75th percentile - 25th percentile
What are two characteristics of a normal distribution?
symmetrical, unimodal, asymptotic
mean, median, mode in same place, middle of the distribution
Define z-score and give the formula for z-score.
z-score represents a raw score in standard deviation terms. number of standard deviations a score is from the mean.
z score = (X-M) / SD
define nominal variable and give an example
used to label data without providing any quantitative value. cannot be ordered or measured. categories.
gender, hair color, etc.
What are the three measures of central tendency?What is the definition of each measure of central tendency?
mean- average of all scores
median- point where 50% of data falls above and below. middle score, average of the two middle scores
mode- score that occurs the most often
Define standard deviation. What is the formula for standard deviation of a population?
The average distance of scores from the mean.
Formula- on board
Give an example of a human trait that produces a normal-ish curve. Explain
height, birthweight of newborns
calculate the z-score given x=6, the mean is 7, and the standard deviation is 2.
explain what this score means
-0.5
This score is half of a standard deviation below the mean.
List the four scales of measurement. Which chart would you use for each?
Nominal - bar graph
Ordinal - bar graph
Interval - histogram
Ratio - histogram
Which measure of central tendency is most impacted by outliers?
Mean
What do measures of variability tell us about a data set? What are the three measures of variability?
Variability tells us about the spread of scores.
Range, Variance, Standard deviation
What do the probabilities under the normal curve tell us?
The percentage of data below, above, or between a certain set of scores.
Calculate the percent below a height of 68 inches given the mean is 66 and the standard deviation is 5. Assume this is a normal distribution.
z score = 0.4
percent = 65.54%
Which measurement type is typically used for an independent variable? Which for a dependent variable?
Independent- nominal/categorical
Dependent-interval/ratio/continuous
What is skewness? What causes skew?
1. refers to the distortion/asymmetry of a normal curve, most scores are clustered at one end of the scale with a few extreme scores
2. Outliers
calculate the standard deviation for a sample given n=3, x's= 5,6,7 mean=6
s = 2
Describe a case where you cannot apply normal distribution probabilities to a sample.
when it is not normally distribution (skewed, +/- kurtosis)
If you know that you need to score 1.2 standard deviations above the mean on the GRE to be considered for the clinical psychology graduate program at the University of Toronto and you know the average score is 300 with a standard deviation of 5, what is the minimum score you need to get to be considered?
x = 306
What is the difference between experimental design and correlational design?
experimental design has independent and dependent variables. Experimental uses random assignment. correlational looks at the relationship between variables. Correlational variables are not manipulated.
Given a mean of 2.6 and a median of 2, how would you describe the shape of the distribution?
positively skewed
Identify the median, 25th percentile, and 75th percentile.
on board
How is the normal distribution helpful in interpreting data?
When we apply it to a given sample we can calculate the probability of getting a specific score
Calculate the percent below a weight of 134 pounds given the mean is 147 pounds and the standard deviation is 10 pounds.
z score = -1.3
percent = 9.68%