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Stats 327 > Quiz > Flashcards

Quiz Flashcards

1
Q

What is an observation?

A

An observation is an individual occurrence or instance that we are interested in

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2
Q

What is a variable?

A

A variable is a characteristic or outcome that can vary from observation to observation

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3
Q

What is data?

A

Data is a collection of recorded information on one or more variables for a set of observations

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4
Q

What are the general types of variables? Define.

A

Qualitative (categorical) variables) are those that classify observations into one of a group of categories. Think “quality” or “what type”

Quantitative (numerical) variables are those that can be measured on a naturally numerical scale. Think “quantity” or “how much”

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5
Q

What are the types of quantitative variables?

A

Steps vs ramp

Discrete variables take on a countable number of values in a given range. You could list or count all the possible values or outcomes for a variable (steps)

A continuous variable is a variable that can take on an infinite number of values ina given range, thus every value within range i a possible value.
Think ramp

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6
Q

What are the levels of measurement?

A

NOIR
Nominal
Ordinal
Interval
Ratio

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7
Q

What is a nominal scale?

A

One that classifies observations into one of a group of mutually expansive categories that cannot be meaningfully ranked or ordered

Ie: religions: Jewish, muslin, Christian

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8
Q

What is an ordinal scale?

A

One that classifies observations into one of a group of mutually exclusive categories that have meaningful rank or order

Finishing first or second in a race
Mood/ pain scales

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9
Q

What is interval scale?

A

Like ordinal scale, but the difference between any two values is the same. Interval scales have no “mathematically meaningful” zero/ the most you can do with an interval scale is measure the difference between who observations

Ex. Celsius, IQ scores

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10
Q

What is the ratio scale?

A

The same as interval scale except that there is a “mathematically meaningful” zero. That is, when you have 0 on a ratio-scaled variable, it means that there is none of the variable

Ex. Number of children, weight

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11
Q

What is a population?

A

A set of all observations we are interested in when we study the behaviour of a variable

Pop size = N

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12
Q

What is a sample?

A

A select subset of observations from teh population, usually much smaller than the population itself
‘
Denoted n

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13
Q

What are the different sampling techniques?

A

Random sampling:
- Simple random sample (SRS)
- Stratified sampling
- Cluster sampling
- Systematic sampling

Non-random sampling:
- convienice sampling
- voluntary sampling

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14
Q

What is simple random sampling?

A

Random sampling
Every conceivable subgroup of n observations has the same chance as being selected for the sample size of n. A random number generated is required.

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15
Q

What is stratified sampling?

A

Random sampling
Done when the population of interest contains naturally occurring groups (or strata) of observations that are similar on one or more characteristics. Obtained by selecting observations from each strata and combining them in a sample

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16
Q

What is cluster sampling?

A

Random sampling
Done when the population of interest contains naturally occurring clusters that do not greatly differ from cluster to cluster but contain observations with differing characteristics. Obtained by selecting one of these clusters as the sample.

17
Q

What is systematic sampling?

A

(1-n-k sampling)
Random
Is done when every kth observation is selected from a list of N observations in a population. A systematic sample comprises every kth selected observation

18
Q

What is convenience sampling?

A

Non-random
When the observations selected for the sample are simply those that are easiest to reach

19
Q

What is voluntary sampling?

A

Non-random
Done when the observations (people) “volunteer” to be in the sample

20
Q

What are the types of sampling bias?

A

Sampling (or selection) bias
Non response bias
Measurement bias

21
Q

What is sampling bias?

A

Occurs when a subset of the population has a lower or higher chance of being selected for a sample compared to the rest of the population

22
Q

What is non-response bias?

A

Occurs when a response is not recorded (for whatever reason) form some portion of the sample

23
Q

What is measurement bias?

A

Occurs when a false/incorrect/untrue response is obtained from a portion of the sample

24
Q

What is a controlled experiment?

A

Establishes a cause and effect relationship between an explanatory (independent) variable and a supposed response (dependant) variable
Established in a controlled setting
There is a treatment and control group

25
Q

What is an observational study?

A

“Hands off”
Researchers do not interfere with with the individuals in the sample, but simple record information on the variables of interest
Cannot be used to establish a cause and effect relationship between two variables, only some association between them

26
Q

What is a lurking variable ?

A

A variable that can affect the response variable but is not accounted for by a study’s design.

27
Q

What is an explanatory vs a response variable?

A

Explanatory (independent) - type one that is suspected to explain or cause changes in the other

Response (dependant) - the variable that is suspected to gained due to the changes in the explanatory variable

28
Q

How do you fill in a frequency table?

A

R: table()

Using the sample proportion formula p^
P = X/n
X+ number of observations in category
N = sample size

29
Q

What is a sample proportion? How do you find it?

A

A ratio or fraction of a sample

P = X/n
X= number of observations in a particular category
n = sample size

30
Q

How do you compute upper and lower fences?

A

Upper fence = Q3 +1.5 (IQR)
Lower fence = Q1– 1.5(IQR)

31
Q

What are measures of central tendency? Measures of variation (spread)?

A

Measures of central tendency describe the tendency of the variables to center or cluster about certain values (mean (x^—), median(x^~)

Measures of variation describes the variation of the observation about a measure of central tendency (variance (s^2), standard deviation (s))

32
Q

What summary values are appropriate for a symmetrical distribution?

A

Central tendency = mean (x^—)

Spread: variance or standard deviation (s or s^2)

33
Q

What is the most appropriate summery of values for skewed graphs?

A

Central tendency: median (x^~)

Measure of spread: IQR

Stats 327 (2 decks)

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