PY 211 learning checks
When cumulating frequencies from the top down, you typically want to discuss the data in forms of:
"at or above"
A researcher measures the following data: 3, 3, 3, 4, 4, and 4. What is the sample variance for these data?
0.3
The sum of relative frequencies across all intervals is equal to _____
1.00
a researcher measures the following scores: 12,14,16,18 and 20. Compute the SS for these data
40
What is the recommended number of intervals that should be included in a simple frequency distribution?
5 to 20 intervals
a researcher collects two samples of data. he finds the first sample (n=8) has a mean of 5; the second sample (n=2) has mean of 10. What is the weighted mean of these samples?
6.0
a researcher selects a population of eight scores where SS =72. What is the population variance in this example?
9
cumulative frequencies can be added from the top ____ and the bottom ____.
down ; up
true or false: a relative percent sums to the total frequency count
false, a relative percent sums to 100%
true or false: qualitative variables can be continuous or discrete
false, can only be discrete
true or false: histograms are used to summarize ungrouped data, which is why each vertical rectangle touches the other
false, histograms are used to summarize grouped data
true or false: the mean is a preferred measure for describing skewed distributions
false, the median is preferred measure
True or false: when the mean is greater than the mode, the distribution is negatively skewed.
false, when the mean is less than the mode, the distribution is negatively skewed
a researcher records the number of times that 10 times cough during a final exam. he records the following data: 0,0,0,3,3,5,5,7,8,and 11. True or false: in this example, the range will be smaller than the interquartile range
false: the range will be larger than the IQR
what is the formula for computing the range
largest value - smallest value
the standard deviation is a measure used to determine the average distance that each score deviates from ____.
the mean
What are two characteristics of rating scales that allow researchers to use these values on an interval scale of measurement?
values on an interval scale are assumed to be equidistant but do not have a true zero
_____ is a measure of the dispersion or spread of scores in a distribution and ranges from 0 to + infinity
variability
Why do we square each deviation in the numerator of variance?
we want to compute how far scores are from their mean without ending up with a solution equal to zero every time and taking the squarement of variance can connect squaring each deviation in the numerator
continuous or discrete: number of questions that participants ask during a research study
discrete
a researcher measures four variables: age (in days), speed (in seconds), height (in inches), and movie ratings (from 1to 4 stars). Which of these variables is not an example of a variable measured on a scale ratio?
Movie ratings
____ symbolizes the size of a population, whereas ____ symbolizes the size pf a sample
N ; n
Describe the sum of squares (SS) in words
SS is the sum of the square deviations of scores from their mean
_____ is the study of phenomena through strict observations,evalutation, interpretation, and theoretical explanantion
Science
a set of data is normally distributed with a mean equal to 10 and a standard deviation equal to 3. Compute a z transformation for each of the following scores in this normal distribution? a) -2 b) 10 c) 3 d) 15 e) 0
a) -4.00 b)0 c)-2.33 d)2.00 e)-3.33
find the probability of a score at or above the following: a) 1.23 b) -2.50 c)0.50
a) .1093 b) .9938 c) .3085
find the probability of.a score between the following z scores a) the mean and 1.40 b) -1.00 and 1.00 c) 60 and 1.20
a) .4192 b) .6826 c) .1592
find the probability of a. score at or below the following z scores: a) 0.08 b) -1.00 c) 2.90
a) .5319 b) .1587 c).9981
State whether each of the following describes an experiment, a quasi experiment or a correlation method a) a researcher tests whether dosage level of some drug (low, high) causes significant differences in health b) a researcher tests whether citizens of differing political affiliations(republican, Democrat) will show differences in attitudes toward morality c) a researcher measures the relationship between annual income and life satisfaction
a) experiment b) quasi experiment c) correlation method
state whether each of the following is an appropriate probability a) p=.88 b)p=-.26 c) p=1.45 d) p=1.00
a) yes b) no c) no d) yes
How many scores are free to vary in a sample?
all scores, except one are free to vary
All of the following are rules for constructing histograms except: a) a vertical rectangle represents each interval, and the height of the rectangle equals the frequency recorded for each interval b) the base of each rectangle begins and ends at the upper and lower boundaries of each interval c) each rectangle represents the frequency of all scores in a distribution d) each rectangle touches adjacent rectangles at the boundaries of each interval
c
all measures of central tendency have a tendency to be at or near the ____ of a distribution
center
the ____ is the preferred measure of central tendency when a data set has outliers
median
a norm distribution has a mean equal to 5. What is the value of the median and mode in this distribution?
median = 5 mode =5
A researcher is interested in the effects of suffering on social behavior with children. He records the number of peers a child speaks to during a typical school day. In this example, would the data be qualitative or quantitative?
quantitative
qualitative or quantitative: delay (in seconds) it takes drivers to make a left-hand turn when a light turns green
quantitative
quantitative or qualitative: number of questions that participants ask during a research study
quantitative
when data are divided into four equal parts, the data are split into ______.
quantities
______ are procedures used to summarize, organiz, and make sense of a set of scores called data
descriptive statistics
continuous or discrete: season of birth (spring, summer, fall, or winter)
discrete
continuous or discrete: type of drug use (none,infrequesnt,moderate,or frequent)
discrete
a _____ is a summary display for a distribution of data organized in terms of how often (or frequently) scores occur
frequency distribution
a(n) ____ is a dot-and-line graph plotted at the midpoint of each interval, whereas a(n) ____ is a dot-and-line graph plotted at the upper boundary of each interval
frequency poly ; ogive
the ___ is the value in a data set that occurs most often or most frequently
mode
distinguish between a random event and a fixed event
outcomes in a random event can vary whereas a fixed event are always the same
____ are rules for how the properties of numbers can change different uses
scales of measurement
an instructor measures the following quiz scores: 6,8,7,and 9 (SD= 1.29). if the instructor subtracts two points from each quiz score, how will the value for the standard deviation change?
standard deviation will not change
state the two steps for locating the cutoff score for a given proportion of data
step 1: locate the z score associated with given proportion in the unit normal table step 2:transform the z score into a raw score
How do you compute standard deviation?
take the square root of the variance
How is the computational formula different from the definitional formula for variance?
the computational formula dAaAoes not require that we compute the mean of compute SS in the numerator
How does calculating the sample variance differ from the population variance?
the denominator for sample variance is (n-1) not N
the calculation of a population mean and sample mean is the same. State in words how to compute the mean
the man is the sum of a set of scores divided by the total number of scores summed
suppose that you sum the squared differences of scores from their mean. What is always true about the result you obtain?
the result is the smallest possible positive solution. subsequently any constant (other than the mean) will produce a larger result
a student scores in the 80th percentile on an exam. What does this mean in comparison to all other students?
the student scored higher than 80% of all others who took the same exam
state the characteristic of the mean that indicates that the mean is the "zero point" for a distribution of scores
the sum of the differences of scores from their mean is zero
the notation used in the formulas for sample mean and population means differs. What notation differs in these formulas?
the term N is used in the denominator for the population mean, and the term n is used in the denominator for the sample mean
a researcher observes the following data set: 3,5,4,4,6,7,8,2,3,2,4,2,2. How many modes are in the distribution? state the value of each move
there are two modes (2 and 4)
a researcher measures the following sample of scores (n=3): 1,4,and 7 a) use the definitional formula to calculate variance b) use the computational formula to calculate variance c) are your answers the same?
a) 9 b) 9 c) yes
identify the column in the unit normal table for each of the following a) the z score b) tje area from each z score toward the tail c) the area between each z score and the mean
a) column b) column C c) column b
a researcher has participants complete a computer task where they can choose to play one of 200 games. Of the 200 games, only 83 are set up so that participants can win the game a) what is the event in this ecample b) what is the outcome x, in this example? c) what is the probability that a participant will choose a game that he or she can win?
a) selecting one game b) seleting a game that a participant can win c) .40
what are the z scores associated with the following probabilities toward the tail in a normal distribution a) .4013 b).3050 c) .0250 d) .0505
a) z= 0.25 b) z= 0.51 c) z= 1.96 d) z=1.64
state the z score that most closely approximates the following probabilities a) top 10% of scores b) bottom 10% of scores c) top 50% of scores
a) z= 1.28 b) z=1.28 c) z=0
which will have no effect on the mean? a) delete a score below the mean b) add a score below the mean c) add a score exactly equal to the mean d) none of the above
c
state the two steps for locating the proportion of scores in any normal distributions
1. transform a raw score into z score 2. locate the corresponding probability for that z score in the unit normal table
cumulative relative frequencies sum to ___ (give or take rounding error)
1.00
how many standard deviations from the mean will contain at least 99% of data for any type of distribution?
10
the population variance is 121. What is the standard deviation for this population?
11
the sample variance is 121. What is the standard deviation for this sample?
11
which of the following will increase value of mean? a) delete a score below the mean b) add a score below the mean c) add a score exactly equal to the mean d) none of the above
a
a psychologist wants to study a small population of 40 students in a local private school. If the researcher was interested in selecting the entire population students for this study, then how many students must the psychologists include?
all 40 students, because all students constitute the population
which of the following will decrease the value of the mean? a) delete a score below the mean b) add a score below the mean c) add a score exactly equal to the mean d) none of the above
b
_____ are graphical displays similar to histograms, except that the vertical bars or rectangles do not touch
bar chart
Why is the variance a preferred measure of variability?
because it clouds all scores in its computation
each of the following is a characteristic of standard deviation except: a) the standard deviation is always positive b) the standard deviation is affected by the value of every score in a distribution c)the standard deviation is used to describe the qualitative variables d) standard deviations are almost always reported with the mean
c
continuous or discrete: delay (in seconds) it takes drivers to make a left-hand turn when a light turns green
continuous
a ___ is a summery display that distributes the sum of frequencies across a series of intervals
cumulative frequency distribution
What the of distribution is used to approximate the median?
cumulative percent distribution
an ogive graphically summarizes what type of frequency distribution
cumulative percent distribution
all of the following characteristics are true about a normal distribution except: a) the mean can be any positive or negative number b) the variance can be any positive number c) the shape of the normal distribution is symmetrical d) the tails of a normal distribution touch the x-axis at 3 SD from the mean
d
each of the following is a rule for the simple frequency distribution except: a) each interval is equidistant b) the same score cannot occur in more than one interval c) each interval is defined (it has a. lower or an upper boundary) d) the interval width is equal to the number of intervals in a frequency distribution
d
the mean is a preferred descriptive statistic: a) for describing normal distributions b) for summarizing interval scale measures c) for summarizing ratio scale measures d) all of the above
d
when cumulating frequencies from the bottom up, you typically want to discuss the data in terms of: a) "at most" b) "less than" c) "at or below" d) all of the above
d
complete the following sentence: the normal distribution is used to determine the probability of a certain outcome ____ to all other outcomes
in relation of relative
Why is it generally inappropriate to include an open interval in a simple frequency distribution?
including an open interval can make it difficult if outliers exist in the data set
A scientist records the following sample. score (n=6): 3, 6, 4, 1, 10, and 12. What is the sample mean of these scores?
m=6.0
the empirical rule is stated for data with what type of distribution?
nominal distribution
which type of model distribution would not be describes using the mode?
nonmodial
What term is often used to describee behavior that fails within 2 SD of the mean in a normal distribution?
normal or statisical norm?
in the following bar chart summarizing the frequency of exercise among a sample of college students, which category of exercise has the largest frequency?
once a week
in 2010, Fortune magazine ranked Apple as the most admired country in the world;d. the rank is on a(n) _____ scale of measurement
ordinal
____ describes characteristics in a population whereas ___ describes characteristics in a sample
parameters; statistics
_____ is the proportion or fraction of times an outcome is likely to occur
probability
the area under a normal curve ranges between 0 and 1 and can never be negative. What type of statistic also has these same characteristics?
probability
quantitative or qualitative: season of birth (spring, summer, fall, or winter)
qualitative
quantitative or qualitative: type of drug use (none,infrequesnt,moderate,or frequent)
qualitative
a researcher collects the following scores: 1,2,3,4,5,6,7, and 8. What is the range of these scores
range = 8-1 =7
Relative frequencies are commonly reported in academic journals as percents. Why?
readers often find percents easier to read than decimals
When would a researcher construct a relative frequency table?
to summarize large data sets
True or false: when all scores in a population are the same, the variance will always be equal to 0.
true
true or false: a ratio scale variable can be continuous or discrete
true
true or false: a researcher observes that a single parent works 42.25 hours per week. The degree of accuracy is 42.25 is to the hundredths place (.01)
true
true or false: an experiment is the only method that can demonstrate cause-and-effect relationships between variables
true
true or false: cumulative relative frequencies are added from the top down or the bottom up
true
true or false: inferential statistics are used to help the researcher infer the unknown parameters in a given population
true
true or false: the 360 degrease in a pie chart correspond to 100% of a data distribution
true
true or false: the sample variance is unbiased when dividing SS by (n-1)
true
true or false: whether you cumulate a frequency distribution from the bottom up or the top down depends on how you want to discuss the data
true
true or false: with identical data sets, the definitional and computational formula for sample variance will always produce the same solution, give or take rounding error
true
true or false: a scientist measures the following data: 23, 23, 23, 23, 23, and 23. The value for the sample variance and population variance will be the same
true because the variance is 0
What are the data called when the frequency of each individual score or category is listed?
ungrouped data
the ___ is the combined mean of two or more groups of scores in which the number of scores in each group is disproportionate or unequal
weighted mean
When is it appropriate to summarize frequencies for ungrouped data?
when data sets only have a few different scores and for qualitative or categorical variables
identify the mode: a study reports that women are more likely to ask for directions than men
women
A researcher records five scores: 3,4,5,6,and x. If the men in this distribution is 5, then what is the value for x?
x=7