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Biol 315 - Bio stats > Module 2 > Flashcards

Module 2 Flashcards

Chapters 6 and 14

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1
Q

Define “Null Hypothesis”

What does it mean in terms of deviation if data?

A

Specific statement, interested to reject. The hypothesis being tested.
-Any deviation from precited data is due to sampling error

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2
Q

Define “Alternative hypothesis”

What does it mean in terms of deviation from data?

A

Non-specific statement, anything but the null hypothesis outcome.
-Anyd aviation from data is not due to sampling error alone

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3
Q

Define “ Two-tailed (sided) hypothesis”

A

Hypothesis that allows for two possibilities (left or right movement in the distribution)

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4
Q

Define “one-tailed (sided) hypothesis”

A

Hypothesis that has only one possibility.

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5
Q

What are the steps for hypothesis testing?

A
  1. State hypotheses
  2. Compute the tests statistic
  3. Determine P value
  4. Draw conclusion
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6
Q

Define “Test statistic”

A

Number calculated from data using a statistical test. Allows for null H to be rejected/ fail to be rejected.

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7
Q

Define “Null distribution”

A

The sampling distribution under the null hypothesis

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8
Q

What is the significance level?

A

Probability value sd in combination with the p-value to decide whether or not the hypothesis can be rejected (Value under 0.05 in this course)

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9
Q

Define a “Type I error”.
What would be a solution?
What is the problem with said solution?

A

Rejecting a true null hypothesis

  • Solution = reduce P from 0.05 to 0.01
  • Problem = increases chances of type II error.
  • alpha
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10
Q

Define a “Type II error”. What is the relationship between this type of error and power?

A

Failing to reject a false null hypothesis.

  • Lower probability of type II error = Higher power
  • Beta
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11
Q

Define “Power” of a study.

What does it tell us about a study?

A

The probability of rejecting a false null hypothesis.

  • More power means a more credible study.
  • more power, higher probability of committing a type 1 error.

**Look at formula

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12
Q

Define “P”

A

Probability of obtaining the null hypothesis aligning data/ probability of obtaining values as extreme/more extreme than the expected values.

Probability of obtaining the expected data or more extreme values .

P = (sum of observed and more extreme values) x 2 **If bell shaped (null) distribution.

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13
Q

What are some factors that increase the power of a study?

A

Higher sample size, low variability.

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14
Q

Define a “nonsignificant result”

A

When the null hypothesis is not rejected. Treat experiment as default.

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15
Q

Define a “Clinical trial”

A

an experimental study involving humans and at least 2 treatments

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16
Q

Define “Confounding variables”

A

Variable that masks or distorts the casual relationship between measured variables in the study.
ex. Increase in temp (confounding variable) increasing both ice cream consumptions and crime rate, making it seem like ice cram consumption increases crime rates.

17
Q

How is the correlation caused by confounding variables torn apart? What effect remains?

A

Random assignment dilutes the correlation. Does not eliminate variation introduced by confounding variable.

18
Q

Define “experimental artifacts”

A

Bias introduced by unintended consequences of unnatural conditions in the experimental procedure

19
Q

How can we deal with experimental artifacts?

A

Conduct experiments under conditions as natural to the subject as possible

20
Q

What is an experimental (simultaneous) control group?

A

Group of subjects subjected to the same technique for assigning treatment as experimental subjects, except they do not receive he actual treatment.

21
Q

Define “Pseudo-replication” . What are the 2 types?

A

occurs when independent replicates are not identified correctly.
-2 types: time autocorrelated and spatial autocorrelated

22
Q

What are the 3 elements that reduce bias in an experiment?

A
  1. Simultaneous control group
  2. Randomization
  3. Blinding
23
Q

Define “blinding” and the 2 different types

A

Concealing information from participants and researchers.

types are single blind and double blind.

24
Q

What is a single blind experiment?

A

Participants are unaware of their treatment assignment.

25
Q

What is a double blind experiment?

A

Participants and researchers are unaware of the assignment of treatments.

26
Q

What are the three elements needed to reduce the influence of sampling error in an experiment?

A
  1. Replication
  2. Balance
  3. Blocking
27
Q

Define “Replication”

A

The application of every treatment to multiple, independent experimental units.

28
Q

What is the purpose of replication?

A

To reduce the effect of variability.

29
Q

Define “balance”

A

All treatments in an experiment are have equal sample sizes.

30
Q

Define “blocking”

A

Dividing experimental units into blocks (groups) based on the sharing of a common feature.
Ex. nesting area.
-Exps must be designed to avoid contamination.

31
Q

How are treatments assigned in a blocking system?

A

Within each block, treatments are randomly assigned to experimental units.

32
Q

Define an “extreme treatment”

A

A strategy used to enhance the probability of detecting differences in an experiment. Makes differences more noticeable.

33
Q

Define “Factor”

A

A single treatment variable , purpose of the experiment is to test its effects.

34
Q

Define “matching”. What is its purpose? When is it used?

A

A strategy that pairs an individual in a target group with a corresponding healthy (control) individual with the same measurements for confounding variables.

  • Purpose: to identify results that aren’t due to confounding variables.
  • Used when randomization cannot be used.
35
Q

Define “statistical significance”

A

Means that the null hypothesis has been rejected

*Often confused for biological importance.

36
Q

Define “biological importance”

A

Expected effect is large enough to matter to truly affect something in the relationship world

37
Q

Define “Placebo effect”

A

An improvement in medical condition that results from the psychological effects of medical treatment.

38
Q

What are the 2 goals of an experiment?

A

To reduce bias and decrease sampling error.

39
Q

What is the purpose of a control group? (3)

A

To control for the effects of time, the placebo effect, and to measure any experimental artifacts.

Biol 315 - Bio stats (3 decks)

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