Module 15: Inferential statistics Flashcards

1
Q

What is the difference between descriptive statistics and inferential statistics?

A

Descriptive statistics is summarizing or describing data from popylations and inferential stats is maing inferences from distributions (analyze samplings to make predictions about larger populations)

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2
Q

The normal distribution

A

Desccribes a very common probability distribution of values of a continous variable around the mean, no skew

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3
Q

Graph of a normal distribution is called

A

The normal curve

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4
Q

Vertical axis of the normal curve

A

Frequency of values

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5
Q

Horizontal axis of the normal curve

A

Scale of continous values, what we are measuring

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6
Q

Properties of a normal distribution (4)

A
  • symmetrical
  • unimodal
  • bell shaped curve
  • mean mode and median are equal
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7
Q

Spread of normal distribution is determined by—– larger spread means —–

A

standard deviation
larger SD

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8
Q

About —% of the data lie within 1 SD of the mean

A

68%

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9
Q

About —% of the data lie within 2 SD of the mean

A

95%

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10
Q

About —% of the data lie within 3 SD of the mean

A

99.7%

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11
Q

The standard normal distribution

A

A normal distribution with a mean of 0 and a standard deviation of 1

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12
Q

Properties of the standard normal deviation (2)

A
  • The cumulative area is close to 0 for Z scores close to z=+/- 3.49
  • The cumulaytive area increases as the Z score increases
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13
Q

Z-table

A

Table with pre-calculated areas under the curve up to each value for Z for a standard normal distribution

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14
Q

Standardization+formula (2)

A

Turning data into a standard normal distribution
- use the formula z=(x-mean)/SD

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15
Q

If you are trying to find the Z score for anything below the mean, your 2 scores should be

A

negative

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16
Q

a Z score of -3.45 means

A

more than 3 SD below the mean

17
Q

Z score tells us

A

how many units you go above and below the SD

18
Q

Larger proportion is —- side for + Z score and —- for - Z score

A
  • left
  • right
19
Q

Percentile always mean

A

everything from the far most left side until that said percetile.

20
Q

Areas are never

A

> 1

21
Q

sampling error

A

Random variability between observations or statistics that is simply due to chance

22
Q

Sampling Distribution + formed when (2)

A
  • The distribution of a statistic over repeated sampling from a specified population
  • Formed when samples of sample size n are repeatedly taken from a population
23
Q

The central limit theorem

A

The larger the sample size that we draw from a population the more normal the sampling distribution of the sample mean becomes, regardless of the shape of population

24
Q

If we take samples of this distribution, cailate their means and then graph them as long as those sampels are big enough >=30, then when we graph that sample distribution it would be —- and centered around —-

A
  • normally distributed
  • population mean
25
Q

Greater the sample size, the more precise/less variability in the

A

sample means

26
Q

You can only use Zed tables when

A

it is normally distributed

27
Q

If the population itself is normally distributed, the sampling distribution of the sample means is —– for any —-

A
  • normally distributed
  • sample size n
28
Q

In both case where you have sample >=30 or a normal distribution, according to the CLT, the sampling distribution of sample means has (3):

A
  1. A mean equal to the population mean
  2. A variance equal to 1/n times the variance of the population
  3. A standard deviation equal to the population SD divided by the square root of n
29
Q

SD and variane of pop and sample formulas:

A
30
Q

Zed score formula for transforming single scores and sample mean into a zed score:

A