H355 quiz 2
What is the weakness of using range?
based on only 2 scores
interquartile range
the range of the middle 50% of the cases
not normal
the two thirds rule does not apply if the distribution is
x-axis
the variable measures first is placed on the
mutually exclusive
these are the result of chance and are independent of each other
S or ó
these symbols are used to represent the standard deviation of the scores of a population.
scattergram
this is a graphic representation of the relationship between two variables.
4.5
what is the IQ range of these scores: 10,10,11,12,13,13,14,14,15
6.5
what is the IQ range of these scores: 5, 5,0,1,2,11,11,11,10,9,7,6,5,5,0,4
biased
a researcher wishes to generalize to all sociology students and uses volunteers in a sociology class as subjects. is the sample biased or unbiased?
normal distribution
about two-thirds of the cases lie within one standard deviation unit of the mean in a
samples of convience
accidental samples
no
according to the 1% guideline should 0.1056 be classified as an unlikely event?
yes
according to the 5% guideline should 0.0446 be classified as an unlikely event?
-3.00
according to this topic, z-scores are seldom lower than what value?
perfect negative relationship
-1.00 indicates a _______ the strongest possible inverse relationship
non directional hypothesis
alternative hypothesis that states that group X on average is different from group y in an unspecified direction.
perfect positive correlation
1.00 indicates- the strongest possible direct relationship
no
an investigator has studied all the girls and boys in a population. she has found a difference between the mean for boys and the mean for girls. is the null hypothesis a viable hypothesis?
computational formula
another formula for standard deviation
approximate 95% rule
approximately 95% of the cases lie within two standard deviation units of the mean in a normal distribution.
how to find the interquartile range
1. put the scores in order from high to low. Then, determine how many scores constitute one quarter of the scores 2. count up from the lowest score the number of scores you calculated in step 1. 3. count down from the highest score the number of scores you calculated in step one. 4. subtract the answer to step 2 from the answer to step 3. this gives you the value of the interquartile range.
false
using a very large sample is an effective way to reduce the errors created by a bias in sampling. is this true or false?
99.7%
if you go out 3 standard deviation units on both sides of the mean in a normal distribution, what percentage of the cases will be captured?
equal
in a scattergram the two axes lengths are
experiment
in order to determine cause and effect, a controlled experiment is needed
variation
If S equals 0 then there is no
7
What is the range of these scores:6,8,8,10,12,13
above the mean
a positive z-score indicates that a person is
properties of a Pearson r
• it can range only from -1.00 to 1.00 • -1.00 indicates a perfect negative relationship- the strongest possible inverse relationship • 1.00 indicates a perfect positive relationship-the strongest possible direct relationship • 0.00 indicates a complete absence of relationship • the closer a value is to 0.00, the weaker the relationship • the closer a value is to -1.00 to 1.00 the stronger the relationship
68%
____ of the cases lie within one standard deviation unit in a normal curve
below the mean
a negative z-score indicates that a person is
50%
a person with a z-score of 0.00 has a score that is higher than what percentage of the group in a normal distribution?
84%
a person with a z-score of 1.00 has a score that is higher than what percentage of the group in a normal distribution?
very strong
a positive scattergram is
one-tailed probability
a question asked only about the upper tail of the normal distribution- the right side
range
a simple statistic that describes variability
extremely weak relationship
a value of r=-.01 represents an
almost perfect relationship
a value of r=-.99 represents an
68%
if the mean for a group equals 27 and the standard deviation equals 3.00, what percentage of cases in a normal distribution lies between 24 and 30?
34%
if the mean for a group equals 40.00 and the standard deviation equals 5.00, what percentage of the cases in a normal distribution lies between 40 and 45?
no relationship
if there is no pattern it is said to be
no
if two groups are equal on average, will they necessarily be equal in their variability?
68%
if you go out 1 standard deviation unit on both sides of the mean in a normal distribution, what percentage of the cases will be captured?
what is a better measurement of variability?
interquartile range
r2
is r or r2 a more direct indicator of variance accounted for
interquartile range
is the range or interquartile range a better measure of variability?
Spread and dispersion
other names for variability
inverse relationship
pattern is from upper left to lower right
volunteerism
people who participate and refuse to participate
intersect
place 1 dot where the two scores for each individual intersects
sampling errors
random errors
sampling errors
random or chance errors
statistacally significant
rejecting the null hypothesis is declaring a result to be
type 1 error
rejecting the null hypothesis when it is true
directional hypothesis
research hypothesis that indicates the direction of the difference
non directional hypothesis
researcher believes there is a difference between scores but there is insufficient information to hypothesize as to which groups achievement is higher
variability
the differences among scores (how much they vary from each other)
curvilinear relationship
the dots form a curve that, starting from the left, goes up for awhile then turns downward
linear relationship
the dots form a pattern that follows a single straight line.
correlation
the extent to which two sets of scores are related.
standard deviation
the larger the deviations from the mean, the larger the
norm-reference interpretation
the norms for normal, below average, and above average, based on what has been commonly observed among large numbers of patients, provide reference points for interpreting raw scores.
raw scores
the number of points earned
alpha level
the probability at which researchers are willing to reject the null hypothesis
standard deviation
this is a measure of how much scores differ from the mean of the scores.
direct relationship (positive)
those who score high on one variable tend to score high on the other
inverse or negative relationship
those who score high on one variable tend to score low on the other
4.41
to two decimal places what is the standard deviation of these scores: 0,2,5,9?
1.72
to two decimal places, what is the standard deviation of these scores: 3,5,6,7,8?
97.50%
to two decimal places, what percentage of the cases in a norm distribution lie below a z-score of 1.96?
84.13%
to two decimal places, what percentage of the cases in a normal distribution lie above a z-score of -1.00?
68.26%
to two decimal places, what percentage of the cases in a normal distribution lie between a z-score of 1.00 and a z-score of -1.00?
95.00%
to two decimal places, what percentage of the cases in a normal distribution lie between a z-score of 1.96 and a z-score of -1.96?
coefficient of determination
useful when interpreting a Pearson r
3.00
what is the highest value in the effective range of z-scores?
3
what is the multiplier for the 99.7% rule?
2
what is the multiplier for the approximate 95% rule?
null hypothesis
what is the name of the hypothesis that says "the true difference between the means equals zero?"
2
what is the outlier in this set of scores: 2,18,18,20,20,21,22
0.0885
what is the probability of drawing a subject with a z-score of 1.35 or higher at random from a normal distribution?
0.0025
what is the probability that 2 and 8 will be drawn in a given lottery in which there are 20 numbers in play on each draw?
r2
what is the symbol for coefficient of determination
x
what is the symbol for the deviation of a score from its mean?
50%
what percentage of participants is encompassed by the interquartile range?
raw score
what term is used to refer to the number of points earned by an individual?
0
when all the scores are the same, the standard deviation equals
variability
when the median is reported as the average for a set of scores, it is customary to report the interquartile range as a measure of
positive relationship
when the pattern goes from the lower left corner to the lower right in a scattergram
many
when working with hundreds of participants, should an investigator expect many or few exceptions to an overall trend?
two-tailed probability
when you ask about the odds of drawing an individual at either tail of the normal distribution
bias
whenever some members of a population have a greater chance of being selected for inclusion in the sample than others
-2.52
if M=511.12 and S=20.28 and Sarah has a raw score of 460, what is the value of her z-score?
-1.00
if M=95 and S=5 and Jake has a raw score of 90, what is the value of his z-score?
0.0769
if a deck of 52 cards is shuffled, what is a probability, expressed as a proportion, that any of the for aces will be drawn?
above
if a person has a z-score of 1.50, is that persons score above or below the mean of the group?
.06
if r=.24, what is the value for r2
no
if r=.66, is the majority of the variance on one variable accounted for by the variance on the other?
77%
if r=.88, what percentage of the variance on one variable is accounted for by the variance on the other?
10%
if r=.95, what percentage of the variance on one variable is not accounted for by the variance on the other?
0.00
if something is certain not to occur the probability of non occurrence is ____
2
how many scores for each individual are required for a scattergram to be drawn?
1.00
if something is certain to occur, the probability of its occurrence is ____
standard scores
help interpret raw scores by indicating where an individual stands in a group.
.001 level
highly significant- reject the null hypothesis with even more confidence
what a standard score indicates
how many standard deviation units a person's score is from the mean and whether his score is above or below the mean
true
adding individuals produces diminishing returns in terms of reducing sampling errors. true or false?
population b
assume that population A has very little variability and that population B has much variability. for which population would a larger sample be needed for precise results to be achieved?
0.92
if M=42.35 and S=2.87 and June has a raw score of 45, what is the value of her z-score?
no
can a researcher be certain that there are no sampling errors if he or she uses random sampling?
variance
differences among the scores
null hypothesis
differences between the two scores due only to errors created by random sampling
simple random sampling
each member of a population is given an equal.chance to be selected
false
establishing a correlation establishes a causal relationship-true or false?
type 2 error
failing to reject the null hypothesis when, in reality, it is false
95%
for M=100.00 and SD=10.00, approximately what percentage of the cases lie between 80.00 and 120.00?
41-69
for M=55 and SD=7, between what two values do approximately 95% of the cases lie in a normal distribution?
45-135
for M=90 and SD=15, between which two values do approximately 99.7% of the cases lie in a normal distribution?
0.0668
for a normal distribution with a means of 100.00 and a standard deviation of 16, what is the one tailed probability of drawing a subject with a score of 124 or greater at random from a normal distribution?
6
for all practical purposes, the normal curve has how many standard deviation units?
false
for an r of .55, 55% of the variance on one variable is accounted for by the variance on the other. true or false?
99.7% rule
going up and down three standard deviation units from the mean identifies where 99.7% of the cases lie.
figure
label the scattergram as a ____ and give it a number and a brief title
.01 level
more significant- reject the null hypothesis with more confidence
where raw scores come from
multiple-choice tests, instruments that measure blood pressure, point systems for creativity in an artistic endeavor, essay examinations, etc...
.06+ level
not significant-do not reject null hypothesis
scattergram
scatter diagram and scatterplot are also names for a
outliers
scores that lie outside of the range of the vast majority of the scores and can greatly increase the size of the range
.05 level
significant- reject the null hypothesis
mean
standard deviation is also reported with the
z-scores
standard scores are also called
Pearson r
statistic for describing the relationship between two sets of scores
How do you find range?
subtract the lowest score from the highest score
parameters
summarized result of a population
statistics
summarized result of a sample
parameters
suppose a population of first grade teachers in a school district way surveyed on their attitudes toward a curriculum change, and all of the teachers in a population participated. the percentages were computed. are the percentages statistics or parameters?
p
symbol for probability
median
the IQ range is associated with which average?
