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Pharmacy Biostatistics > Bivariate Analysis: Independent T-Test and ANOVA > Flashcards

Bivariate Analysis: Independent T-Test and ANOVA Flashcards

1
Q

What is an Independent T-Test?

A

Measures a Continuous variable and compared across two Discrete independent groups

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2
Q

What is a Two Group Comparison research design entail?

A

1 Group receives an experimental treatment
1 Group receives a placebo or usual care

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3
Q

What does the independent variable measure in an Independent T-Test?

A

Discrete, nominal

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4
Q

What does the dependent variable measure in an Independent T-Test?

A

Continuous, ratio

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5
Q

What factors influence the size of t in an Independent T-Test?

A
  1. Difference between the means (X1-X2)
  2. Variability (sp2)
  3. Sample Size (n)
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6
Q

How does the Difference between the Means change t?

A

As the difference between the mean increases, the value of t increases

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7
Q

How does the Variability change t?

A

As variability value increases, the value of t decreases

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8
Q

How does the Sample Size change t?

A

As the sample increases, the value of t increases

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9
Q

In an Independent T-Test the hypothesis includes what?

A

The comparison of means between independent groups

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10
Q

What is an ANOVA test?

A

Measures a continuous variable, compared across 3 or more Discrete Independent groups

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11
Q

ANOVA is a 2 Step Process, what are the steps?

A
  1. Test for differences among the group means
  2. If yes, then a follow up test to identify which specific groups are different from one another
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12
Q

What are the assumptions that must be made to complete an ANOVA test?

A
  1. Random Samples
  2. Independent Samples
  3. Independent observations within groups
  4. Normally distributed data
  5. Equal variances
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13
Q

What is the first step of the ANOVA?

A

F Test for H0: no difference among group means

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14
Q

The F Test for H0 looks at what?

A

F-Statistic
P-Value
If p-value is less than significance level, reject H0

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15
Q

What is the second step of the ANOVA?

A

Post Hoc* Test

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16
Q

The Post Hoc* Test is what?

A

Modified version of T-Test, pairwise comparisons
Post Hoc = After the event

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17
Q

What is a Familywise Type 1 Error Rate?

A

The probability of making at least one type 1 error when multiple tests are conducted on the same variable in independent samples increases with each additional test

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18
Q

What tests corrects for the Familywise Type 1 Error Rate?

A

Post Hoc

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19
Q

What does the HA of an ANOVA test suggest?

A

At least ONE population mean does not equal another population mean

20
Q

If you reject the null hypothesis, you can conclude that at least one population mean is different but it cannot conclude that ALL of the population means are different? You must use what test to analyze this?

A

Post Hoc, used to determine which specific means are different

21
Q

What are the 2 sources of Variance in an ANOVA test?

A
  1. Between: variance between the various groups
  2. Within: variance within each group
22
Q

What is the Total Variance?

A

Variance between groups + Variance within groups

23
Q

How do you partition variances?

A

Alleviate negative numbers by squaring
Sum of squares

24
Q

What is SSB?

A

Sum of the square differences BETWEEN the group means and the grand mean

25
Q

How do you calculate the SSB?

A
  1. Subtract grand mean from each group mean and square
  2. Sum the numbers
  3. Multiply the sum by the sample size
26
Q

SSB contains what information?

A

EFFECT
aka treatment effect

27
Q

What is SSW?

A

Sum of all the square differences between individual data and the group mean WITHIN each group

28
Q

How do you calculate the SSW?

A
  1. Calculate each group mean
  2. Subtract individual observation from its group mean and square
  3. Sum all numbers
29
Q

SSW contains what information?

A

ERROR
takes into account the error within the groups

30
Q

What is the partitioning of the sum of squares?

A

SSB (SSEffects) + SSW (SSError) = SS (Total)

31
Q

What is MSB?

A

Mean Square Between Groups

32
Q

What does MSB describe?

A

Average deviation of group means from the grand mean

33
Q

How is MSB calculated?

A

Unbiased estimate of error variance plus treatment

34
Q

What is MSW?

A

Mean Square Within Groups

35
Q

What does MSW describe?

A

Average deviation of means from their group mean

36
Q

MSW = MSE, which is what?

A

Mean Square Error

37
Q

How is the F-Statistic calculated?

A

F Stat = MSB/MSW

38
Q

For any treatment to have an effect, F must be greater than what?

A

Greater than 1, cannot be negative

39
Q

F Statistic represents what?

A

Ratio of treatment effect to error

40
Q

If the population means are equal, the sample means will be close together suggesting what type of data?

A
  1. Sample means will be close to grand mean
  2. SSB and MSB will be small if population means are equal
  3. Small F Stat
41
Q

If at least one population mean is quite different, the corresponding sample mean will be different suggesting what type of data?

A
  1. Corresponding sample mean will be different from grand mean
  2. SSB and MSB will be large
  3. Large F providing evidence against H0
42
Q

How large is F Stat required to be in order to reject H0?

A
  1. Determine by F Critical Value associated with DF and Alpha
  2. Determined by the p-value associated with the calculated f-stat (Large F = small p-value)
43
Q

ANOVA F-Tests are ALWAYS ONE SIDED for determining what?

A

P-Value

44
Q

But for an ANOVA can a one sided HA be used?

A

NO, must be 2 sided

45
Q

What is Eta-Squared n^2?

A

Tells you the strength of the relationship between independent and dependent variables

46
Q

Eta-Squared percentage reveals the variance that can be explained

A

ex. Eta=22%
100-22 = 78
78% of variance results from other factors

Pharmacy Biostatistics (17 decks)

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