BioStatistics exam 3- Q’s and A’s
T/F Two samples will probably have different means even if they are both the
same size and they are both selected from the same population? - - True
- A researcher selects a sample and administers a treatment to the
individuals in the sample. If the sample is used for a hypothesis test, what
does the null hypothesis (Ho) says about the treatment? - - the treatment
has no effect on the scores
- if a hypothesis test produces a z score in the critical region, what decision
should be made? - - reject the null hypothesis
- accurately describe a hypothesis test - - an inferential technique that uses
that data from a sample to draw inferences about a population
- accurately describe the critical region - - outcomes with very low
probability if the null hypothesis is true
- a sample of n=25 individuals is selected from a population with u=70, and
a treatment is administered to the sample. What is expected if the treatment
actually has no effect? - - the sample mean should be close to 70 and should
lead you to fail to reject the null hypothesis
- what is an accurate definition of a type 1 error? - - rejecting a true null
hypothesis
- the critical boundaries for a hypothesis test are z= +/- 1.96 . If the z score
for the sample data is z = +/- 1.89, what should be done? - - fail to reject the
null hypothesis (Ho)
- what is the first step in a hypothesis test - - state your hypotheses
- what is the second step in the hypothesis test - - set your decision criteria
- what is the third step in the hypothesis test - - collect data and calculate
- what is the fourth step in the hypothesis test - - make a decision based on
your results
- under what circumstances can a very small treatment effect still be
significant - - if the sample size (n) is very large
- what is an accurate definition form the power of a statistical test? - - the
probability of rejecting a false null hypothesis
, - what will increase the power of a statistical test - - changing the sample
size from n=20 to n=100
- when n is small (less than 30), how does the shape of the t distribution
compare to the normal distribution? - - it is flatter and more spread out than
the normal distribution
- on average, what value is expected for the t statistic when the null
hypothesis is true - - 0
- if two samples are selected from the same population, under what
circumstances will the two samples have exactly the same t statistic? - - if
the samples are the same size and they have the same mean and the same
variance
- (solve) a sample of n=9 scores has a variance = 36. what is the estimated
standard error for the sample? - - Sm= √(variance/n) = 2
- (solve) a researcher conducts a hypothesis test using a sample from an
unknown population. If the t statistic has df=30, how many individuals were
in the sample? - - {df= n-1 } >>> n=31
- With alpha= 0.05 and df = 8, the critical values for a two tailed t test are t
= +/- 2.306. Assuming all other factors are held constant, if the df value is
increased to df = 20, what would happen to the critical values for t? - - they
would decrease (move closer to zero)
- if other factors are held constant, what is the effect of increasing the
sample size? - - it will decrease the estimated standard error and increase
the likelihood of rejecting the null hypothesis (Ho)
- If an independent-measures design is being used to compare whether diet
or exercise modification is more effective for weight loss, then how many
different groups of participants would be needed and how many scores
would there be for each participant? - - 2 groups, 1 score each
- (solve) an independent-measures study used n=15 participants in each
group to compare two treatment conditions. what is the df value for the t-
statistic for this study? - - (df1+ df2) = n-2 = 28
- (solve) a researcher reports t(22) = 5.30, p < 0.05 for an independent-
measures experiment. how many individuals participated in the entire
experiment? - - t(df) ...df=n-2 ...=24
T/F Two samples will probably have different means even if they are both the
same size and they are both selected from the same population? - - True
- A researcher selects a sample and administers a treatment to the
individuals in the sample. If the sample is used for a hypothesis test, what
does the null hypothesis (Ho) says about the treatment? - - the treatment
has no effect on the scores
- if a hypothesis test produces a z score in the critical region, what decision
should be made? - - reject the null hypothesis
- accurately describe a hypothesis test - - an inferential technique that uses
that data from a sample to draw inferences about a population
- accurately describe the critical region - - outcomes with very low
probability if the null hypothesis is true
- a sample of n=25 individuals is selected from a population with u=70, and
a treatment is administered to the sample. What is expected if the treatment
actually has no effect? - - the sample mean should be close to 70 and should
lead you to fail to reject the null hypothesis
- what is an accurate definition of a type 1 error? - - rejecting a true null
hypothesis
- the critical boundaries for a hypothesis test are z= +/- 1.96 . If the z score
for the sample data is z = +/- 1.89, what should be done? - - fail to reject the
null hypothesis (Ho)
- what is the first step in a hypothesis test - - state your hypotheses
- what is the second step in the hypothesis test - - set your decision criteria
- what is the third step in the hypothesis test - - collect data and calculate
- what is the fourth step in the hypothesis test - - make a decision based on
your results
- under what circumstances can a very small treatment effect still be
significant - - if the sample size (n) is very large
- what is an accurate definition form the power of a statistical test? - - the
probability of rejecting a false null hypothesis
, - what will increase the power of a statistical test - - changing the sample
size from n=20 to n=100
- when n is small (less than 30), how does the shape of the t distribution
compare to the normal distribution? - - it is flatter and more spread out than
the normal distribution
- on average, what value is expected for the t statistic when the null
hypothesis is true - - 0
- if two samples are selected from the same population, under what
circumstances will the two samples have exactly the same t statistic? - - if
the samples are the same size and they have the same mean and the same
variance
- (solve) a sample of n=9 scores has a variance = 36. what is the estimated
standard error for the sample? - - Sm= √(variance/n) = 2
- (solve) a researcher conducts a hypothesis test using a sample from an
unknown population. If the t statistic has df=30, how many individuals were
in the sample? - - {df= n-1 } >>> n=31
- With alpha= 0.05 and df = 8, the critical values for a two tailed t test are t
= +/- 2.306. Assuming all other factors are held constant, if the df value is
increased to df = 20, what would happen to the critical values for t? - - they
would decrease (move closer to zero)
- if other factors are held constant, what is the effect of increasing the
sample size? - - it will decrease the estimated standard error and increase
the likelihood of rejecting the null hypothesis (Ho)
- If an independent-measures design is being used to compare whether diet
or exercise modification is more effective for weight loss, then how many
different groups of participants would be needed and how many scores
would there be for each participant? - - 2 groups, 1 score each
- (solve) an independent-measures study used n=15 participants in each
group to compare two treatment conditions. what is the df value for the t-
statistic for this study? - - (df1+ df2) = n-2 = 28
- (solve) a researcher reports t(22) = 5.30, p < 0.05 for an independent-
measures experiment. how many individuals participated in the entire
experiment? - - t(df) ...df=n-2 ...=24
