Brainscape's Knowledge GenomeTM

Browse over 1 million classes created by top students, professors, publishers, and experts.


See full index

Stat 1000 > Unit 3 > Flashcards

Unit 3 Flashcards

1
Q

what is a population?

A

a collection of objects about which we want information

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
2
Q

what is a sample?

A

a part of the population consisting of units we actually examine to gather information

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
3
Q

what are the two types of sampling that is bias?

A

voluntary response samples and convenience samples

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
4
Q

what is voluntary response sampling?

A

when people make the choice of whether or not they want to participate

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
5
Q

what is the problem with voluntary response sampling? how is it bias?

A

usually only people with very strong opinions will bother to phone in and vote, others that dont care will exclude themselves from the sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
6
Q

what is an example of voluntary response sampling?

A

newspaper publishes a survey, there is a phone number to phone in and vote

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
7
Q

what is convenience sampling?

A

when you select a sample based on how convenient it is for you (the one gathering the sample)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
8
Q

what is the problem with convenience sampling? how is it bias?

A

not everyone has the chance of being selected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
9
Q

what is an example of convenience sampling?

A

if we wanted to know if the students like the hours of the library and we stand in university centre and asked the students that were walking by

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
10
Q

how do we overcome bias?

A

select a sample by “chance”

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
11
Q

what are the 5 unbiased forms of sampling?

A

simple random sampling
stratified
multistage
systematic
census

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
12
Q

what is the strong statement of simple random sampling?

A

SRS of size n consists of n individuals from the population chosen in such a way that every group of n individuals has an equal chance to be the sample actually selected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
13
Q

what is the weak statement of simple random sampling?

A

using simple random sample guarantees that every unit in the population has an equal chance of being chosen for the sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
14
Q

what is the definition of stratified random sampling?

A

we divide the population into strata, then we choose an SRS from within each stratum to form our full sample

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
15
Q

what is an example of stratified random sampling?

A

if we want to know how Canadian’s feel about taxes, there is a natural division to this population between provinces and territories and they all pay a different amount of taxes. we would then take a simple random sample from each stratum (province) and then combine responses

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
16
Q

what is the benefit of stratified random sampling over an SRS?

A

SRS can sometimes give you insufficient sample size in some of the strata which affects the ability to make conclusions about those strata

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
17
Q

when do we use multistage sampling?

A

if we need to select smaller and smaller groups from the population and we can employ different sampling techniques at each stage

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
18
Q

what is an example of multistage sampling?

A

if we want to conduct a poll looking into poverty in a third world country, we first select an SRS of villages from the list of all villages, then we select a sample of blocks from these selected villages, then select a sample of households from these blocks

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
19
Q

is multistage, just as good as SRS? why?

A

no, because not all units have the same chance of being included and not every combination of units has a chance of being selected

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
20
Q

look at the difference between SRS, stratified and multistage *SRS, Stratified and Multistage

A
How well did you know this?
1
Not at all
2
3
4
5
Perfectly
21
Q

what is systematic random sample? explain how it works.

A

in this sampling procedure, we start with a numbered list of all N individuals in the population. to select a sample of n individuals, we randomly select a number from 1 to k, where k= N/n. the sample then consists of the k th individual on the list and every k th individual after that.

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
22
Q

what is an example of systematic random sample?

A

a teacher wants to select a random sample of five of her 40 students in her class to participate in a demonstration.
to do this she randomly selects a number from 1 to 8, she selects the student in that position on the class list and every 8 th student after that
ex. she selects the number 3 (randomly) then she will select student 11, then 19, then 27, then 35

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
23
Q

is a systematic random sample a SRS?

A

no, because not every group is equally likely to be chosen (for example, the first 8 students wouldn’t all be able to be in a group)

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
24
Q

what is the biggest advantage of a systematic sample?

A

it is easy and fast to select
dont always need a list of the entire population

How well did you know this?
1
Not at all
2
3
4
5
Perfectly
25
Q

in what circumstance would we not use a systematic random sample?

A

when there is a pattern in the population list (for example, the days of the week)

26
Q

what is census sampling?

A

collection of data from every individual in the entire pooulation

27
Q

what is the best way to sample?

A

census (we don’t use it because its very costly)

28
Q

what are 3 types of bias?

A

undercoverage
non response
response bias

29
Q

what is undercoverage?

A

list from where the sample is drawn is incomplete
ex. you cold call landlines, not everyone has a landline anymore

30
Q

what is non response?

A

people may refuse to answer
mail in surveys have a low rate of return

31
Q

what is response bias?

A

people may lie
they may not remember what their answer was
question is poorly worded

32
Q

what are 6 things to remember in selecting a “good sample”?

A

select the sample in an unbiased manner
proper interviewer training
non-leading questions
try to make non- response not an issue
include all population units in your possible sample
voluntary response and convenience response are not appropriate

33
Q

broadly speaking what are two ways we can obtain data?

A

we can sample units from a larger population and just simply observe some characteristic of these sampled units (cant impose a cause and effect relationship)
we can carry out an experiment where we observe the response to some treatment imposed on the units
(can impose a cause and effect relationship)

34
Q

what is a cause and effect relationship?

A

Causality is a relationship between two variables, in which one event or process causes an effect on the other event or process.
For example, research tells us that there is a positive correlation between ice cream sales and sunburns. Meaning, as ice cream sales increase, so do instances of sunburns.

35
Q

what is the one reason why we wouldn’t be able to conclude a cause and effect relationship between two variables?

A

if its a poorly designed experiment

36
Q

what happens in an observational study?

A

the researcher simply observes the units or subjects, and measures the variables or characteristics of interest
(the researcher DOES NOT actively interfere with the units)

37
Q

what happens in an experimental study?

A

the researcher imposes some treatment on the units or individuals
(imposes the values of x)

38
Q

experimental units

A

the objects on which our experiment is being conducted. (if the experiment is done on humans, they are referred to as subjects)

39
Q

factors

A

the explanatory variables (they will explain) in an experiment (ex. amt of sleep you get)

40
Q

levels or factor levels

A

individual values of the factors

41
Q

treatment

A

a specific experimental condition applied to the units (they’re combinations of factor levels)

42
Q

response variable

A

the variable that is measured following the application of a treatment

43
Q

what does randomization do to treatment groups?

A

makes them as similar as possible (this is a good thing)

44
Q

what is a completely randomized design?

A

an experimental design that randomly assigns treatments to the experimental units

45
Q

lurking variable

A

anything you’re not studying

46
Q

what is an example of a lurking variable?

A

picking people based on what time they show up to work, the lurking variable would be that the people that show up earlier are normally more motivated

47
Q

why is random allocation important?

A

because it eliminates the effect of any other lurking variable

48
Q

a well designed experiment implements a control, what is it?

A

a mechanism to minimize the effects of other variables (besides the factors) on the response variable

49
Q

what are the 4 methods of control?

A

comparison of two or more treatments in the same environment
use of a control group
double- blinding
blocking

50
Q

when is a treatment group required and not required?

A

required when there is only one other treatment group
not required if there are at least two other treatment groups

51
Q

biased form of sampling example in respect to a new medication

A

when a medical company wants to show that its new medication really works, they give it to the sickest patients who will tend to show the most improvement

52
Q

double blind experiment

A

an experiment in which neither the subject nor the person administering the treatment knows which treatment is the one being applied at any time

53
Q

single blind

A

when only one person knows

54
Q

what does the double blind method reduce?

A

the placebo effect and biased interpretations of the results

55
Q

replication

A

repeat each treatment on many subjects so as to reduce variation in the results

56
Q

randomization

A

using chance to assign experimental units to treatments

57
Q

what is blocking?

A

a group of experimental units that are similar in a way that may affect the responses

58
Q

randomized block design

A

when the subjects are divided into blocks and the treatments are assigned at random within the blocks

59
Q

how are completely randomized design and randomized block design different?

A

randomized block design: randomization occurs within blocks, the blocks are not randomly formed
completely randomized design: randomization occurs when assigning the treatment to the experimental units

60
Q

why is a blocking variable not a factor?

A

because factors are explanatory variables that we would like to study for their impact on the response variable

61
Q

what is the purpose of an experiment?

A

to avoid confounding and to establish causation

62
Q

a good experiment will…. (7)

A

-allocate units to treatments randomly
-control the effect of possible lurking variables (by comparing different treatments or using control groups)
-use replication to apply each treatment to several individuals
-draw a diagram of the design to better explain it
-eliminate bias by conducting a double-blind experiment if possible
-remember the placebo effect when inferring causation
-use a randomized block design if some units are similar with respect to the response variable

Stat 1000 (5 decks)

Brainscape helps you reach your goals faster, through stronger study habits.
© 2024 Bold Learning Solutions. Terms and Conditions