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Statistics for Psychology ch 1-4
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Terms in this set (72)
Data
Facts and statistics collected together for reference or analysis
Variable
any characteristic that can take on different values.
Ex: height score on exam, gender
In a study on a perception of facial expressions, participants must classify emotions displayed in photographs of people as anger, sadness, joy etc.
"Type of emotional Expression" is measured on a(n) ____________Scale?
*what is the "variable" in the study?
emotional expression
*What are the possible "values"?
anger, sadness, joy etc. -categories
Nominal variables (non numeric)
"values" are categories
ex: gender (m/f), religion, ethnicity etc.
nominal variable (categorical)
variable with values that are categories or names (non numeric)
numeric variable also called quantitative
Variable whose values are numbers with meaning; two types: 1) rank order (ordinal) 2) equal interval variables
What type of variable is "eye color" be?
Nominal variable
rank-order variable (ordinal variable)
numeric variable in which the values are ranks, such as class standing, place finished in a race or birth order. Ranked without size, faster or slower only 1st,2nd,3rd.
equal-interval variable
variable in which the numbers stand for approximately equal amounts of what is being measured;
Ex: Temperature; GPA Height; Inches on a ruler; difference between 2.0-3.0 GPA is exactly 1.0
A survey of adults in a city are asked to report the number of children they have. Number of children is measured on a(n)_________scale
On a rank order or equal interval scale?
How do you know?variable in the study?
What are the possible values?
equal interval scale
Variable is: number of children
no difference between these intervals
A survey of adults in a city are asked to report about themselves, including identifying their SES status as upper, middle and lower class. SES is measured on a(n)_________scale
On a rank order or equal interval scale?
How do you know?
What are the possible values?
rank ordered scale
Variable in the study is SES
Lower, middle and upper class
Are the differences between these values all necessarily equal? NO
organizing and displaying data frequency tables; Three types:
1) ungrouped frequency table
2) grouped frequency table
3) graphs
ungrouped frequency distribution table
a count of how often each individual value of a variable occurs in a set of data.
Make a list of all possible values, ordering scores, from lowest to highest even if one number was not used in your set (value 70x0) 68,69,71,72...(70 is missing show x0) show all other values each time a set occurs in its frequency.
% for each score; Divide the total number of scores ex: (1/4)(100)=25%
Histogram
A graph of vertical bars representing the frequency distribution of a set of data.
bimodal distribution
a frequency distribution having two values (two peaks) with the greatest frequency. On the highest point of the graph.
ex; height in a sample w/ males & females
symmetry
balanced proportions
Unimodal
one peak ex; test scores
Rectangular mode
ex; number of children in a classroom
Midpoint
A point that divides a segment into two congruent segments
Bar Graph (Histogram)
a graph that uses vertical or horizontal bars to show comparisons among two or more items; eye color (nominal variable) bars do not touch.
Population
A set of ALL individuals of interest in a research study selected from population.
random sampling
a method of poll selection that gives each person in a group the same chance of being selected.
margin of error
an amount (usually small) that is allowed for in case of miscalculation or change of circumstances in a poll.
non random or haphazard
Every member of the population does not have an equal chance of being selected.
This is referred to as haphazard or biased sampling.
If a student wants t conduct test on volunteers to take part in a study is that a
Random, haphazard, specified, or quota?
Haphazard selection
If a student wants to study alcohol of High School students and obtains a list from a local school of ALL students enrolled, place the names in a hat and select as many needed for the study. What kind of test is that
Random, haphazard, specified, or quota?
Random
inferential statistics
numerical data that allow one to generalize- to infer from sample data the probability of something being true of a population
Mean
Average of all the scores, total. Obtained by adding the scores and then dividing by the number of scores
Median
Middle number
Mode
The value that occurs most frequently in a given data set.
Calculating Mode
To calculate the mode arrange all the numbers from lowest to highest. Find the number (or numbers) that show up the most often.
Find the median: 21, 32, 45, 60, 13, 25
However many numbers 6+1/2=7/2=3.5
add to the 3rd and 5th number and divide by 2 if its an EVEN amount of numbers
45+13/2=29=median
When it's an ODD go to the middle number add 1 and divide by 2=Median
standard deviation
the square root of the variance
Symmetrical Data
Mean, median, and mode are roughly the same, data is distributed evenly
skewed distribution
a representation of scores that lack symmetry around their average value
skewed right "positively" skewed
A skewed distribution with a tail that stretches right, toward the larger values.
ex; a difficult test score
Tail is where the fewest scores are.
kurtotic distribution
heavily tailed peak (bell shaped)
ex; some housing markets
Light tailed or flat ex; years of education
(college)
A prison psychologist recorded the number of rule infraction for 15 prison inmates (over a six month period to be: 5,4,2,4,3,5,2,0,4,4,5,5,3,4, and 3
-make Frequency table
-sketch Histogram based on frequency table
-describe in words the shape of histogram
(negatively or positively skewed right or left symmetrical)
**note make a frequency table
'Value" refers to what's being measured or "X" in this case # of infractions.
Value___________Frequency______%
"X"=15 infractions
f
r
e
q
u 3
e 2
n 1
c 0 0 1 2 3
y Rule infractions
Adding a new score to a distribution will always change the mean? T/F
False
Changing the value of a score within a distribution will almost always change the mean? T/F
True
A distribution has a mean of 80 (M=80). If 6 points were added to every score, what would be the value for the new mean?
86
Which of the following distributions would contain the LEAST amount of variability?
an alpha distribution, a bell or normal distribution, a "thin" distribution, or a "flat" distribution
A "thin" distribution
A study involved measuring the number of days absent from work for employees at a large company during the preceding year. The researcher reported the mean to be 9.00 with a standard deviation of 6.0. First, what symbols would you use to stand for the "9" and "6". Second, explain in words what these two numbers mean (sentence or two).
M= 9; SD= 6
*The average number of days employees were absent from work was 9 last year. On average, (scores) number of days absent deviated from the mean by 6 days.
Which measure of central tendency will be most affected if one extremely large score is added to a distribution?
The mean
In a perfectly symmetrical, unimodal distribution, the mean, median and mode will have the same value? T/F
True
Which measure of variability is more commonly reported? The Variance or the SD? Why?
The SD, bc it is based on actual, non squared units, so it's more interpretable than the variance.
What does it mean for a sample to have a SD of zero? Of five?
Zero: Scores do not deviate from the mean; They are all equal; there is no variability in the set data.
Five: On average, the scores in the data set deviate from the mean by five points.
When a distribution is skewed to the left (negatively skewed)
The median is less than the mean, the mean and the median are the same, the mean and the mode are equal, the mean is less than the median
The mean is less than the median
A negatively skewed distribution of scored with a mean of 40 (M=40) and SD of 8 (SD=8)is transformed into Z-scores. The distribution of Z-score mean of ______and a SD of ______.
The shape of this distribution (above) of Z-scores will be __________
Answer: Mean of Zero and a SD of One
Answer: negatively skewed same as original distribution of "raw" scores.
A z-score = +1.00 indicates a position in a distribution____________
above the mean by a point, above the mean by a distance equal to one st. dev., below the mean by one point, below the mean by a distance equal to 1 standard deviation
above the mean by a distance equal to 1 st. dev.
A negative Z-score always indicates a location below the mean. T/F
True
A score close to the mean has a z-score close to 1.00? T/F
False It would be closer to zero
Assume a person scores 81 on a verbal test ability and a 5 on a test of quantitative ability. For the verbal test, the mean for people in general is 3.40 with a std. dev. of 1.47
What's the persons stronger ability: verbal or quantitative? How do you know
Verbal ability is higher
x - m = 81 - 50 = 1.55 x - m = 5 - 3.4= 1.09
SD 20 SD 1.47
Imagine a student is seeking admission to an MBA program, but the school only considers students who score in the top 30% on leadership skill. If the mean score on the leadership test is 60, the standard deviation is 12 and the distribution is normal, what is the lowest raw score on the test a person could have to be in the top 30%?
70.20, 60.80, 66.24, 50.00
66.24
When a sample score is extreme enough to Reject the Null (falls in rejection region), result is considered?
statistically significant, proven correct, proven incorrect, statistically insignificant
Statistically significant
By convention psychologists consider obtaining a sample score that is less than _______% chance occuring to be unlikely enough that we can reject the Null
5%
A distribution with a mean of 70, a median of 80, and a mode of 85 is probably positively skewed? T/F
*when in doubt draw it out
Mean(70)<Median(80)<Mode(85)
False; It's probably negatively skewed
*when in doubt draw it out; Frequency table.
Mean(70)<Median(80)<Mode(85)
Mode will always "peak" of distribution
When psychologists study a sample to see if it represents a population (called pop 1) that is different from a known population (called Pop 2), the comparison distribution is?
*the same distribution as pop 1
*the same distribution as pop2
*a rectangular distribution with the same mean & SD as pop1
a rectangular distribution with the same mean *and a SD as the unknown Pop
*the same distribution as pop2
a ceiling effect occurs when you have a distribution that is
symmetrical, positively skewed, negatively skewed, or rectangular
Negatively skewed, scores are piled up on the high end; "a floor effect" is the opposite.
skewed left "negatively" skewed
A skewed distribution with a tail that stretches left, toward smaller values.
ex; an easy test
Tail is where the fewest scores are.
positively skewed distribution
A distribution where the scores pile up on the left side and taper off to the right.
negatively skewed distribution
A distribution in which most scores pile up at the high end of the scale.
ceiling effect
all the scores are piling up together at the high end
rule infraction
the act of breaking a rule
histograms and frequency polygons
common method for displaying frequency information graphically
Dependant variable
what is being measured, behavior or response. We hypothesize that DV is affected by the IV
research design
a detailed plan or method for obtaining data scientifically
Statistics is how data is analyzed
independent variable
variable that is manipulated by the experimenter. Typically divided into two treatment groups: It is controlled and "manipulated" by experimenter. We hypothesize that the affects (causes changes in) the DV
IV: ex. Pop 1: DV:Behavior/
Pop 2: response
A researcher wants to know if the temperature of the room affects how students perform on an exam. What's the IV? What are the two levels? What's the DV?
IV: "Temperature" w/2 levels 1) Hot 2) Cold
DV: Performance on an exam
A researcher wants to know if children perform better in school when they watch educational programs. What's the IV? What are the two levels? What's the DV?
IV: "type of television programs" w/2 levels 1) educational 2) non-educational
DV: Performance in school
A sports psychologist is interested in the effect of electrolyte sports drink on endurance of athletes. A group of 30 athletes is selected and half are given a treadmill endurance test while consuming the sports drink; the other half take the endurance test while drinking water.
What is the pop of interest?
What is the sample?
What is the IV and what are its levels?
What is the DV?
Pop of interest: ALL athletes, or athletes in general.
Sample: The 30 that were tested
IV and levels: type of drink (1:electrolyte sports drink, 2: water)
DV: scores on endurance test
true experimental design
research using an experimental group and a control group, to which test units are randomly assigned and hallmark of cause and effect experiments, accurate measurement of DV.
correlational design non research
Research that examines the relationships between variables, whose purpose is to examine whether and how two variables change together. It can not draw conclusions on cause and effect
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