Chapter 11- sampling, Data Presentation and Interpretation (statistics) Flashcards

1
Q

what is censuses sampling? what are its pros and cons?

A

census sampling is a survey of a whole population.

pros:
1) accurate representation
2) unbiased

cons

1) time, effort and money intensive
2) if members of a population are missed it could be biased
3) if the tested items are used up or damaged its impractical

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2
Q

what is a population?

A

the whole group of people is the population. its finite and countable

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3
Q

what is simple random sampling? what are is pros and cons?

A

simple random sampling is when every person has an equal chance of being chosen in the sample but each selection is independent of the others. often done using a random number generator

pros:
1) completely unbiased if everyone as an equal chance

cons:
1) can be inconvenient if the population is spread over a large area

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4
Q

what is systemic sampling? what are its pros and cons? how to dit?

A

systemic sampling is when every nth member of a population is selected. done by numbering the population from a full list. find a regualr interval. generate a random starting point as your first member of the sample. keep adding he interval to your sample.

pros:
1) can be used effectively in quality control
2 should be unbiased

cons:
1) if the number cosen lines up wit a pattern on the populus then it can be biased

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5
Q

what is stratified sampling? what are the pros and cons?how is it done? what’s the formula?

A

if a population is divided into categories, you can use stratified sampling where the same proportion of each category in the sample in the population is used. to do this divide a population into categories. use the formula to find how many needed for each category. randomly select the sample from each category.

(size of category in population / total population size) x total sample size

pros:
1) if there’s no overlap between them this is a representative sample
2) its useful when results vary depending on categories

cons:
1) can be expensive

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6
Q

what is quota sampling? what are the pros and cons? how is it done?

A

the interviewer is given a quota to fill and they fill it. to choose a quota sample divide a populous into categories. give each category a quota. collect data until quotas are met without using random sampling.

pros:
1) easy for interviewer
2) non response is less of a problem

cons:
1) can be biased. the interviewer may exclude some of the population

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7
Q

what is opportunity sampling? what are its pros and cons? how is it done?

A

opportunity sampling is when he sample is chosen from a section of the population that is most convenient for the sampler. chose members that are easiest to sample.

pros:
1) quick
2) cheap
3) easy

cons:
1) isn’t random
2) can be very biased

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8
Q

what is cluster sampling? pros and cons? how is it done?

A

cluster sampling is when the population is divided into distinct groups. the clusters should be groups you’d expect to give similar data.

to choose a custer sample:
divided the population into clusters covering the whole population, where no member belongs to multiple clusters. randomly select clusters. use either al the members or randomly sample.

pros:
1) practical( quicker and cheaper) for certain situations
2) adaptable as it can incorporate several sampling methods

cons:

1) less representative
2) not always possible to separate into clusters

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9
Q

what is self selection sampling? what are the pros and cons? how is it done?

A

self selection sampling is when people choose to be part of the sample.

how its done:
advertise or appeal to the whole population for participation. Then either use everyone who responds or take a sample of them.

pros:
1) quick and easy
2) non responders are less of a problem
3) it could be the only way to get people to respond

cons:
1) could be trends or strong opinions leading to bias

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10
Q

what are qualitative variables?

A

qualitative variables are non-numerical values

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11
Q

what are quantitative values?

A

quantitative values are values that are numerical

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12
Q

what’s the class width formula?

A

class width = upper class boundary - lower class boundary

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13
Q

what’s the class midpoint formula?

A

midpoint= (lower class boundary + upper class boundary) / 2

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14
Q

what’s the formula for frequency density?

A

frequency density = frequency / class width

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15
Q

what is a stem and leaf diagram?

A

stems leafs

1 137
2 45557
3 98

key:2 1 means 21

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16
Q

what’s the mean equation?

A

mean = sum of x / n

17
Q

what’s the median?

A

The median is the value in the middle of the data set all the data values placed in order of size

18
Q

what is the mode?

A

the mode is the most frequently occurring data

19
Q

what is the modal class?

A

the modal class is the class highest frequency density

20
Q

what is the range?

A

range= highest value - lowest value

21
Q

what is the interquartile range (IQR) ?

A

interquartile range (IQR) = upper quartile (Q3) - lower quartile (Q1)

22
Q

The position of the xth percentile (Px)?

A

xth percentile (Px) is x/100 X total frequency (n)

23
Q

what are outliers?

A

outliers are Q1 - (1.5 X IQR ) Q3 + (1.5 X IQR)

24
Q

Whats the equation for variance?

A

variance = ( x- mean )² / n

25
Q

what’s the equation for standard variation?

A