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74 Cards in this Set

  • Front
  • Back
In statistics what is a population
represents the entire group of indivudals in whom we are interested
B/c it is costly and labourly intensive to study the entire population therefore we collect data on a SAMPLE of indviduals who are
representative of this population we are taking a sample we have introduced sampling error
We are often interested in the value of a parameter in the population (i.e) What is a parameter
numerical
mean or proportion
What is statistics
an estimate of parameters
What is a sampling distribution of the mean
take several separate smaples and each has its own mean, and plot over time--should get a normal distribution
What is a standard error the mean (SEM)
amount of variation in menas between our sample and other repated samples of a fixed size
SEM=
s.d./square root of n

n=sample size
SEM is always <
s.d
SEM is an indicator of precision, the smaller the SEM the
indicates that are estime is more precise
What is the sample distribution fo the proportion
SE(p)= √ P(1-p)/n
ONce we have taken a sample from our popuation we obtain a point estimate (single data) to make an interval estimate b/c
more useful
Confidence intervals
range in which we are 95% sure that the tue value lies between
95% CI for the mean
average +- 1.96(SEM)
CI for the proportion
P +- (SEp)
We often gather sample data in order to assess how much evidence there is against a specific hypothetsis about the popuatlion this is AKA
hypothetisis testing
What are the 5 stages of hypothesis testing
1. Define the Null and alternative hypothesis
2. Collect relevant data
3. Calculate the value of the test statistic specific to Null hypthetsis
4. Compare the values of the test statistic to values from a known probability distruvbtion
5. Interpest P value
What is the null hypothesis or Ho=
the is NO difference in the population
What is the alternative hypothesis
difference does exist in the population
After you collect data from a sample of indivuals then you
calculate the correct statistical test
After you calculate a test statistic, then you then you compare with a known
probability distribution
What is the P value is
the probability of obtaining our results if the null hypotheis is true
THe samller the p-value, the more
UNLIKELY the null is true
What does P <0.05 really mean
the observed result was less then 5% likely to have occur due to chance alone
If P <0.05, the we
REJECT the null hypothesis and conclude there is a real difference
We say we "REJECT the null hypothetisis NOT
accept or proven it
If P is greater or equal to 0.05 then we
FAIL to reject the null hypotheris--NO real difference was found
A small p-value DOES NOT mean that the alternative hypothesis is
TRUE
Does a P value tell us the result are valid
NO
Does the p value tell us the magnitude of effect
NO--how small the p value does not mean anything
Does the P value the probabilty the null hypothesis is true
NO
The p value only tells us
that the observered result was less than 5% to have occur due to chance alone
Why is the two-tailed test the best
NO assumptinos on the direction of effect
Are confidence intervals and hypothesis test closely linked
YES
What is a type 1 error
we reject the null hypothesis when it is tru
What is alpha
is the maximum proability of fasely rejecting the null hypothesis that awe are willing to tolerate
What is alpha=
0.05
What is a type II error
we DO NOT reject the null hypothesis when it is false
What is Beta
maximum probability of flaslsely accepting the null hypothesiis that we are willing to tolerate
1-Beta is the
power of the test to detect if adifference turly exists
B=0.2 what is power
80%
What are factors influencing power
Sample size, increase size increases power
Decrease varailbity increases poewr
increasing effect size increase power
Does the power increase as Type 1 error increase, and why
YES--type II error decreases
What is minimum power needed
70-80% or more
For numerical data what is parametric test for 1 group
one-sample t test
What is the numberical data for NON-parametic test for 1 group
sign test
What is the non-parametric 1 group test
sign test
When do we use non-parametric data
when the data is skewed
Is the data is skewed then we do not use the average, rather
median
What 2 groups for numerical data what are 2 catergoires
pair or independent
What are Paired group
measuring one-group twice---measuring BP twice pre and post
What is test for measuring Paried numerical group
paired t-test
What is the test for measuring NON-parametic pair groups
Wilcoxon signed test ranks
The most common numerical 2 group is
indepenent
What is an example of numuerical parametric 2 group independent
2 groups one given a drug and the other placebo
What is the test used for 2 group independent
unpaired t test
When do have 2 independent group for one to have drug vs placebo what must you first do
ramdonize
Should the average for both drug and placebo be the same for both groups prior to starting
YES
What statistical test is used for 2 independent groups
two sample t-test or (unpaired t-test)
When is the ANOVA test used
3 or more groups
What test is used for 3 or more groups that data is skewed
Kruskal wallis test
What is the test statistic for ANOVA
F ratio
The Global test means if the P value is greater than or equal to 0.05, than
all means are equal
If P values is < 0.05 for ANOVA, what do we do
POST HOC TESt to determine which ones are different
How does the Post Hoc Test determine which one is differnt
using hte Minimum differnt size which is greater than or equal to 5
Categorical data--meaning each inviducal
posses a characterics of intrest (is males, is pregant, died/vs
Catergoical data does NOT use means, rather
proportions
In Categoical datas we are interested in detmerine wether
the TRUE proprotion in the popuation takes a particular value (HAVE DIABETES OR DO NOT HAVE DIABETES)
What is test for ONE group categorical data
z test for proption
What is test for categorical data with 2 groups (paired)
McNemar's test
What is test for categorical data with 2 groups (independent)
Chi-squared test
What must we have to calculate a test statistic for categoical data with 2 indpendent groups
2X2 and the there are mutally exclusive categorical
If a 2x2 and they are mutally exclusive, then you use
Chi-saure test with1 degree of freedom
When you use the Fisher's exact test
sample <5
What test do you use for Categorical data >2 groups
Chi-squared test