psych 311 ch.1-4
a researcher selects a sample of 24 participants and has them complete a survey on dating preferences. in this example, what are the degrees of freedom for sample variance and what does this figure represent?
df = 23 it represents the number of scores that are free to vary in a sample
weighted mean
an arithmetic mean of a weighted to disproportionate set of scores. the weighted mean is used to compute the combined mean for two or more samples of scored n which the number or scored in each sample is disproportionate or unequal.
degrees of freedom for the sample variance
are equal to the sample size minus 1
what terms refer to each of the following measures, respectively: mean, median, mode.
average, middle, most
a researcher records the number of children at a local school from single-, divorced-, and married-parent homes. this frequency data would be best displayed as a
bar chart
adding the same constant to each score in a dist. (or subtracting the same constant from it) will
cause the mean to change by that constant
qualitative data varies by _____________ quantitative data varies by ____________
class amount
__________ is the variable that is believed to change in the presence of the independent variable.
dependent variable
the scale of measurement a researcher uses
determines the type of inferential statistics that can be done
a characteristic (usually numeric) that describes a population is called a
population parameter
a psychologist that reviews her notes for all her patients and determines that on average her patients complete therapy in 24 days. the average time to complete therapy among all her patients is called a
population parameter
three key elements of control that allow researchers to draw cause-and-effect conclusions are
randomization manipulation comparison/control
a researcher compares the amount of college debt (in dollars) that undergraduate students incur up to their four-year degree. college debt is on what scale of measurement?
ratio
to construct a pie chart, first distribute the data as
relative percentages
you are interested in measuring the construct, reinforcement. which of the following measures for this construct is quantitative and continuous?
the size of a reward in grams
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 exam
a professor grades 120 research papers and reports that the average score was an 80%. what do we know about the sum of the differences of these 120 scores from their mean of 80%?
the sum of differences is equal to zero.
an interquartile range removes
the top and bottom 25% of scores in a distribution before calculating range
a percentile point is
the value of a score on a measurement scale below which a specified percentage of scores in a distribution fall
all other things being equal (so assuming that the value of SS never changes), as a sample size increases,
the value of sample variance decreases
mode
the value that occurs most often or at the highest frequency in a dist.
regardless of the number of scores in a dist., the range only includes __________ score(s) in its calculation.
two
characteristics of the mean:
-add a score above the mean and the mean will increase -add a score below the mean and the mean will decrease -delete a score below the mean and the mean will increase
sample variance is
-an unbiased estimator of the population variance -associated with n-1 degrees of freedom -computed by dividing SS by df
a simple frequency distribution
-can be used to summarize grouped data -can be used to summarize ungrouped data -summarizes the frequency of scores in a given category or range
the mode is an appropriate measure of central tendency for
-data that are bimodal -use with other measures of central tendency -data that are on a nominal scale
the mean is an appropriate measure of central tendency for
-data that are normally dist. -data that are on an interval or ratio scale -data in which the mean, median, and mode are equal
the median is an appropriate measure of central tendency for
-data that are positively skewed -data that are negatively skewed -data that are on an ordinal scale
when cumulating frequencies from the top down, the data are discussed in terms of
-greater than -at or above -at least
interval scales of measurement: examples
-marital satisfaction ratings on a 5-point rating scale -the latitude and longitude of birth for those suffering from schizophrenia -the body temp. (degrees F) increase during exercise
descriptive statistics are procedures used to
-summarize a set of scores or observations -organize a set of scores or observations -make sense of a set of scores or observations
a researcher records the following scores: 9.9, 9.8, 9.6, 9.5, 9.7, 9.1, 8.9, 9.8. what is the range for the scores?
1.0 (9.9 to 8.9)
a researcher selects sample of 6 males and 11 females. she asks participants to rate the likelihood they would do female-stereotyped jobs (such as nursing or school teaching) on a scale from [1 = not likely] to [5 = very likely]. men indicated that they would be less likely to do these jobs (M = 2.1) compared with women (M = 4.3). what is the weighted mean for this entire sample of 17 participants?
3.5
the computational formula for variance
-the computational formula will always produce the same solution as the definitional formula (give or take rounding errors). -it is a short-cut method for calculating variance when the population or sample size is large. -it is derived mathematically from the definitional formula.
measures of variability can range in value from
0 to + infinity *(insert infinity symbol)*
rules for constructing a histogram
1) a vertical rectangle represents each interval, and the height of the rectangle equals the frequency recorded for each interval. 2) the base of each rectangle begins and ends at the upper and lower boundaries of each interval. 3) each rectangle touched adjacent rectangles at the boundaries of each interval.
simple frequency distribution for grouped data
1) find the real range 2) find the interval width 3) construct the frequency dist.
finding the percentile point in a cumulative percent dist.
1) identify the interval within which a specified percentile point falls. 2) identify the real range for the interval identified. 3) find the position of the percentile point within the interval. 4) identify the percentile point.
a researcher records the time in seconds it takes a sample of participants to walk alone through a dark portion of campus. the research camputes SS = 1,000. assuming that a sample of 11 participants was observed in this study, what is the standard deviation for this data.
10 seconds
a researcher decided to split scores on an exam into quartiles. she determines that a score of 64 is at the 25th percentile, a score of 74 is at the 50th percentile, and a score of 80 is at the 75th percentile. what is the interquartile range (IQR) for these data?
16
a researcher reports that 12 persons in a sample of 60 reported getting between 4 and 6 hours of sleep per night. What is the relative percentage for this interval?
20%
the empirical rule:
68% of all scores lie within one standard deviation of the mean; 95% of all scores lie within two standard deviations of the mean; 99.7% of all scores lie within three standard deviations of the mean.
which of these scores have the largest variability? A) scores: 1, 3, 6, 9, 12 B) scores: 22, 24, 26, 28, 30 C) scores: 1, 2, 3, 4, 5,
A) scores: 1, 3, 6, 9, 12
a researcher records the following scores on a working memory quiz for two samples. which sample has the largest standard deviation? sample A: 2, 3, 4, 5, 6, 7, 8 sample B: 4, 5, 6, 7, 8, 9, 10
BOTH samples have the same standard deviation
a researcher wants to determine how many participants will take less than 24 seconds to complete a cognitive performance task. if he constructs a frequency dist. for these data, what type of dist. would be more appropriate to answer his question?
a cumulative frequency dist. from the bottom up
operational definition
a procedure that identifies a measurable, observable behavior and uses the resulting measurements as a definition of a hypothetical construct.
the definitional formula ___________ the computational formula for SS.
equals
statistical analysis allows researchers to
evaluate scientific observations
which research design is used to determine the causes of behavior that help to explain why the behavior occurs?
experimental
the three steps for constructing a simple frequency distribution are
find the real range, find the interval width, and construct the frequency distribution
a therapist observes that spouses are more likely to forgive their partners for lying to them if they find out the truth from their spouse and not a third party. in this example, the dependent variable is:
forgiveness
which of the following requires the calculation of a real range?
frequency distributions for grouped data
interval scales of measurement
have equidistant scales
a graphical display for grouped frequency distributions with continuous data is called a
histogram
which of the following is a type of graphical display used to summarize quantitative, continuous data?
histogram frequency data ogive
a researcher asks participants to estimate the calories they consume in a meal. the researcher records the following estimates: 450, 426, 310, 500, 220. if the researcher removes the estimate of 220 (perhaps because the participant drops out of the study), then the value of the mean will
increase
procedures that allow researchers to infer or generalize observations made with samples to the larger population from which they were selected best describes
inferential statistics
the range of scores in each interval of a grouped frequency dist. is called the
interval width
a researcher records the following data: 4, 4, 4, 4, 3. how would you describe the variability of these data?
it is very small (close to 0) because the scores are approximately the same.
in the stem-and-leaf display, each number to the right of the vertical line is referred to as a ________; the numbers to the left of the vertical line are called the __________.
leaf; stem
the sum of the squared differences of scores from their mean is
minimal
a researcher records the hospital admission rates for coronary heart disease at 10 local hospitals. she finds that 2 different hospitals had the highest overall rates of hospital admissions. which measure of central tendency did this researcher use to describe these data?
mode
the variance and standard deviation can never be
negative
a researcher records the following data for a time (in seconds) it takes five rats to cross an electrical grid to obtain reinforcement on the other side: 12, 9, 13, 4, 12. is the mean equal to the mode in this example?
no; the mode is larger than the mean
a researcher distributes frequencies into the following classes: absent, tardy, present. what type of data are distributed?
nominal qualitative ungrouped data
a researcher distributes frequencies into the following intervals: 1-10, 11-20, 21-30, 31-40, 41-50, 51+ what is wrong with this frequency distribution?
one interval is an open class
a consultant ranks the 5 most needed areas of improvement for a local business. what scale of measurement are the rankings?
ordinal
order of operations (in math)
parenthesis roots exponents multiplication division addition subtraction
a researcher asks participants to estimate the height (in inches) of a statue that was in a waiting area. the researcher records the following estimates: 40, 46, 30, 50, 34. if the researcher removes the estimate of 40 (due to an experimenter error) then the value of the mean will ____________ (HINT: calculate the mean first)
remain the same
a researcher measures the number of trials it takes two samples of participants to master a new task. in both samples, SS = 240. sample A consisted of 12 participants and sample B consisted of 18 participants. which sample is associated with the largest variance?
sample A
if a portion of people from a population are asked to complete an assessment, then the average score among the group of people would be considered a
sample mean
a characteristic (usually numeric) that describes a sample is called a
sample statistic
an example of a distribution with NO variability
scores: 5,5,5,5,5,5
a researcher records 52 scores. what is the median position of these scores?
the average of the 26th and 27th scores in numeric order.
bar charts are like histograms EXCEPT
the bars displayed do not touch
a researcher distributed frequencies into the following intervals: 3-6, 7-10, 11-15, 16-18, 19-22, 23-26. what is wrong with this frequency dist.?
the interval width is unequal
median
the middle value in a dist. of scores that are listed in numeric order
you are interested in measuring the construct, work expertise. which of the following measures for this construct is quantitative and discrete?
the number of employees that work under an employee
measures of attraction: an example of a ratio scale measurement
the physical proximity (in feet and inches) between two romantic partners
a researcher reports that "the average shopper in the sample (n=12) purchased $65.00 worth of items (mu=$65.00) during a busy shopping day." what mistake was made in this citation?`
the sample mean is written using the wrong notation
when would a researcher calculate a population mean?
when data are measured for all members of a population
each deviation in the numerator for variance is squared because
without squaring each deviation, the solution for SS would be zero.
a researcher records the following data for the number of dreams recalled during a night of sleep for 10 college students: 3, 2, 4, 4, 3, 1, 1, 0, 2, 0. is the mean equal to the median in this example?
yes
