Understanding Statistics
The null hypothesis says the true difference equals what numerical value
0.05 or less
For a Pearson r of 0.60, what is the value of the coefficient of determination
0.36
when a researcher uses the 0.01 level, what are the odds of making a type 1 error
1 in 100
Name two circumstances under which median > mean for research
1. Ordinal data 2.
Do the following means on a performance test indicate an interaction between type of reward and age? Do the means indicate a main effect for type of reward?
1. Yes 2. No they are the same
What % of the participants lie w/in 1 SD unit of the mean in normal distribution
68%
When consumers of research incoperate proportions, what is a good idea?
Convert into a %
Which branch of statistics (inferential or descriptive) helps researchers to summarize data they can be easily comprehended?
Descriptive
Are % or proportions easier to comprehend?
%
When the relationship between two variables is perfect and inverse, what is the value of r
-1
if individuals in a group have all the same score, what is the SD?
0
what is the base for a proporiton
1
Percentages for different gruops are expressed on a common scale w/ what base
100
If there are means for four gruops (A B C D) there are how many indivdual pairs of means to be compared w/ a multiple comparison test?
4
A Pearson r of 0.70 is what percentage better than a Pearson r of 0
49%
This topic describes how many types of consideration for determing practical significance
5
if p=0.5 for a chi squre test, how many chances in 100 that the null hypothesis is true
5
interquartile range is the range of of what?
50% of the participants using, range between quarters
Do researchers use "univaritate" or Bivariate" to examine relationships between two nominal variables
Bivariate
Which type of analysis classifies participants in terms of two variables in order to examin the relationship between 2 variables
Bivariate Analysis
Are null hypothesis more likely to be explicityly stated in a "journal article' or "dissertation"
Dissertation
according to this topic, ethical considerations should play no role in the interpretation of the results of a study. Is this statement True or false
False
Suppose a researcher reported that for Group X, the median = 55.1 IQR=30, while for group Y median= 62.9, IQR=25. Which group has higher average score? Which group is more variable?
Group X
Which statistics discussed in this topic are measures of variablity
IQR
If a researcher tests a random sample instead of all members, is it likely the sample will be the same as the result the researchers would have obtained by testing the population?
In all likelihood no
Which branch of statistics helps researchers to draw inferences about the effects of sampling errors on their results?
Inferential statistics
Objective, multiple choiced achievement tests are usually assumed to measure at what level
Interval
The number of minutes of overtime work that employees perform is an exmaple of which scaled measurement
Intervals
What do researchers do if the proability is greater than 0.05
It remains on the possible list of explanations why the observed change occurred
Why is random sampling desirable even though it creates errors?
Less bias
What must be done in order to convert a coefficient of determination to a percentage
Must Square "r" to get a value and that can be turned into a percentage
if a distribution is skewed to the left, does it have a positive or negative skew?
Negative
Should determining the practical signifcance of a study's results be be a mechanical process
No
Does a crucial difference need to be numerically large to be of practical significance?
No (e.g. school's student scores crossing a funding threshold)
If a distribution has some extreme scores on the right (but not on the left) it is said to have what type of skew
Positive skew
what does the null hypothesis say about the difference between two sample means
There is no difference
What is the name of the error researchers make when they reject the null hypothesis when in fact it is a correct hypothesis
Type I Error
What is the name of an error researchers make if they fail to reject the full hypothesis when in fact it is an incorrect hypothesis
Type II Error
According to this topic, should client acceptability of a tx e considered when determining practical significance
Yes
If an ANOVA yields p<.05, should the null hypothesis be rejected
Yes
If the cost is very low, might a very small statistically significant difference be of practical significance?
Yes
Is it possible for a small difference to be statitcally significant
Yes
When reporting a percentage, is it a good idea to also report the underlying number of cases
Yes
if a researcher compares two means for significance, wil ANOVA and the t test yield the same probability
Yes, same value of p
What is meant by the term variability
amount by which participants vary or differ from eachother
ANOVA stands for what?
analysis of variance
What is the name of the test of the null hypothesis used in this topic?
chi-square
What is descriptive statistics?
describing the results actually were
is a relationship direct or inverse when those with high scores on one variable have high scores on the other ...visa versa?
direct
inferential statistics
numerical methods used to determine whether research data support a hypothesis or whether results were due to chance
When researchers study a sample, are the results called the "true" or "observed" results?
observed results
what is the symbol for probability
p
Is a researcher found that a chi-square test of a difference yielded a p < 0.05, what should they do?
reject null hypothesis
formal definition of the mean
the value around which the deviations sums to 0
Do researchers reject the null hypothesis when the probability of its truth is "high" or low
Low
which average is defined as the middle score
Median
Which average is defined as the most frequently occuring score?
Mode
if a researcher has four means on an achievement test for samples of students in four states, can he or she determine whether the set of differences, overall is statistically sig by using a t-test? explain. Could a researcher use a ANOVA for the same purpose?
No, t-test can only do two variables. Should be ANOVA
IF a researcher assigns a teacher to rank studenst according to their oral language skills, the researcher is using which scale of measurement
Ordinal
What is the name of the statistic that describes how many participants per 100 have a certain characteristic?
Percentage
Does a distribution w/ a tail to the right have a + or - skew
Positive
In most populations, income has what type of skew
Positive
IF an overall ANOVA for three or more means is significant, it can be followed by what type of test to determine the signifciance of the differences among the individual pairs of means?
Scheffe's test
By studyign samples , do researchers obtain statistics or parameters
Statistics
r=1.00 indicates ...
Strong correlation between the two quantities, one effects the other perfectly
What is an alternative way of saying a researcher has rejected the null hypothesis
The difference is statstically significant at the 0.05 level
Is it possible for two groups to have same mean but different standardizations?
yes
Should median be used for highly skewed distribution
yes
Which average is defined as the balance point in distribution
mean
Which average is usually reported when SD is reported
mean
synonym for averages
mean
should mean or medium be used with ordinal data
median
Which two statistics mentioned in this topic (median and IQR) are averages (i.e. measures of central tendency?
median and IQR
which one of the three averages is very seldom used in formal reports of research
mode
When a researcher uses a large sample, is he more or less liely to reject the null hypothesis
more likely
when the size of the difference between mean is large, is a researcher more or less likely to reject the null hypothesis that when the difference is small
more likely
If a researcher has a statistically sig result, should the null hypothesis remain on the list of viable explanations for an observed differnece
no
If an ANOVA yields p>.05, is/are the differences statistically significant?
no
Should mean be used for highly skewed distribution
no
Does the term "sampling error" refer to random errors or bias
random errors
What scale of measurement has an absolute zero
ratio
suppose a researcher drew random samples of urban, surburban and rural children , tested them for creativity, and obtained three means. Should the researcher do a one or two way ANOVA to test for significance? Why
One way, there is only one variable (location)
Weight measured in pounds is an example of which scale of measurement
Ratio Scale
What two scales of measurement have equal distances among the scores they yeild?
Ratio and interval
What decision should be made about the null hypothesis if a chi-squre test leads to conclusion that observed differences are unlikely to be due to random error
Reject
Significance tests are designed to determine the probabilities regarding the truth of what hypothesis?
The null hypothesis has been rejected or true
What does the null hypothesis say about sampling error?
The observed difference was due to the sampling error
Are significance tests associated w/ descriptive or inferential statistics
inferential
Is margin of error a "descriptive" or an "inferential" statistic
inferential
is range or interquartile range a more reliable statistic
interquartile range
In an ANOVA table, which statistic is of greatest interest to the typical consumer of research?
p value
what should p be to declare a difference statistically significant
p<0.05
Do the following means on an achievement test indicate an interaction between the method of instruction (A vs B) and the aptitude of the students (high vs low) Do the means indicate a main effect for method of instruction? Do the means indicate a main effect for Aptitude?
1. No b/c the method of insturction. 2. Yes 3. No
The middle 68% of the participants in normal distribution have scores between what two values if mean=100, SD 15
85, 115
Describe a hypothetical study in which it would be appropriate to conduct a chi-squre test for univariate data
Living in Idaho and people would fill in Nominal results
According to this topic, should the typical consumer try to interpret the value of df?
No
Are the values of t and df of any special interest to typical consumers of research?
No
If you fail to reject a null hypothesis, is the difference in question statistically significant
No
Should typical consumers of research be conerned w/ the values of the degrees of freedom?
No
t=2, df=20, p>.05 for the difference of the two means. Should the null hypothesis be rejected?
No
If a researcher asks participants to name the country they are born in, what scale of measurement are they using
Nominal
Which scale of measurement is at the lowest level
Nominal
What is the name of the curve that is symmetrical
Normal curve
By studing populations, do researchers obtain "statistics" or parameters"
Parameters
Pearson "r" stands for
a relationship between two quanitative sets of scores they compute a correlation coefficient. The coefficent is r