Lecture 4 - Distributions, Introduction to Experimental Design & Statistics Flashcards

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1
Q

assumption of distribution in the mean:

A

normal

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2
Q

assumption of distribution in the median:

A

none

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3
Q

shape of normal distribution curve:

A

bell-shaped, asymptotic at the extremes, symmetrical at the mean [no skew], mean = median = mode

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4
Q

area under the normal distribution curve is:

A

directly proportional to the relative frequency of observations and their probability: p

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5
Q

relationship between the mean and standard deviation in normal distribution:

A

in a normal distribution, mean and standard deviation are independent of each other: infinitely many possible combinations of mean and standard deviation and hence infinite number of normal distributions possible

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6
Q

standard normal distribution (z-distribution):

A
  • developed to compare all normal distributions
  • a normal distribution with a mean of 0 and a standard deviation of 1
  • area under curve is 1
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7
Q

poisson distribution:

A

often discrete, count data [often plummeting at the bottom]

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8
Q

binomial distribution:

A

proportions, binary variables [e.g. ‘heads & tails’]

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9
Q

statistical hypothesis:

A

statement about the world that can be falsified

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10
Q

null hypothesis (H0):

A

no difference, no relationship, no effect, no signal

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11
Q

alternative hypothesis (H1):

A

[normally our research hypothesis] - signal

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12
Q

Y variable & X variable:

A

Y - response (subject to hypothesis): binary, proportion, continuous, discrete

X - explanatory (object of hypothesis): binary, proportion, continuous, discrete, categorical

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13
Q

what axis/variable is subject of hypothesis?

A

the Y variable

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14
Q

basis of experimental design:

A

manipulation of the explanatory X variable

measure change in the response Y variable

can test for causation

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15
Q

how can we increase the power of an experiment?

A

through decreasing the noise - increasing sample size and randomising

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16
Q

statistical tests have:

A

• A test statistic (e.g. t, F, Chi²) with value
• Degrees of freedom
• P-value, p-value

17
Q

degrees of freedom:

A

number of independent observations minus number of parameters we estimated from the data

18
Q

figure legends:

A

given under the figure and should be informative; i.e. reader needs to understand the figure without reading the main text. All abbreviations etc. need to be explained.Table captions are given before the table

19
Q

mean and SD of standard normal distribution (z-distribution):

A

standard normal distribution (z-distribution) has a mean of 0 and a standard deviation of 1

20
Q

we can compare all normal distributions to the standard normal distribution by:

A

• converting our y into a number of standard deviations from the mean and finding the probability with which this value lies in a range

21
Q

research processes include:

A

formulation of hypotheses, planning of experiment,
summarising & analysing data (descriptive & inferential statistics), interpretation of results

22
Q

large part of the research process involves:

A

hypothesis testing

23
Q

Statistical (null) hypothesis:

A

statement about the world that can be falsified; no signal

24
Q

Alternative hypothesis:

A

signal (often our research hypothesis)

25
Q

what experiments can and can’t test causation?

A

Correlative, descriptive studies cannot test causation; experiments that manipulate the explanatory variable can test causation

26
Q

statistical tests provide:

A

a test statistic with value, degrees of freedom and a p-value

27
Q

p-value:

A

probability of getting a test statistic as large as yours (or higher) if the null hypothesis is true; probability that a null hypothesis (H0) is true

28
Q

how do you calculate the degrees of freedom?

A

number of independent observations - number of parameters we estimated from the data

29
Q

figure legends are given under the inure and should be informative:

A

reader needs to understand the figure without reading the main text

all abbreviations etc. need to be explained, table captions are given before the table

results and methods are written in past tense, give direction of effect, test statistics are given in brackets