Module 1

Question 1

Statistics

Answer 1

study of methods to describe and measure aspects of nature from samples& population

Question 2

Estimation

Answer 2

the process of inferring an unknown quantity of a target population using sample&nbsp

Question 3

Population parameter

Answer 3

all quantities describing populations mostly denoted by greek letters

Question 4

sample statistic

Answer 4

(estimate) is related quantity calculated from a sample, used to estimate the population parameters

Question 5

Sampling unit

Answer 5

the unit/individual/subkect/ replicate that we choose our sample based of

Question 6

Sampling error

Answer 6

the chance difference between an estimate and the population parameter being estimated caused by sampling

Question 7

Precision

Answer 7

less sampling error= higher precision// higher sample size=less sampling error= higher precision

Question 8

Accuracy

Answer 8

when the average of all estimates that we might obtain is centered on the true population value

Question 9

Bias

Answer 9

if sampling process favours some outcomes over others, it might systematically under or overestimate the populaiton parameter

Question 10

Random sample

Answer 10

sample from a population that fulfills two criteria of 1.equal chance of each indiivdual being in sample 2.independent unit( choosing one wont effect others in the study) (snapshot of the entire population)

Question 11

Independent Observations

Answer 11

selection of any member shouldnt effect the chance of other ones (one of the musts for random sampling as well)

Question 12

Sample of convenience

Answer 12

is a collection of indiivudals that are easily available to researcher (most accesible to them)

Question 13

volunteer bias

Answer 13

type of bias in human studies since there might be some systematic differnces in the pool of volunteers

Question 14

Variables

Answer 14

characteristics that differe among individuals or other sampling units

Question 15

Descriptive statistics

Answer 15

quantities that describe the sample
1. frequency distribution
2. measures of location (mean, median, mode)
3. measures
4.measures of shape

Question 16

Standard error

Answer 16

the standard deviation of the sampling distribution of an estimate, it reflects the precision of an estimate low STD=high precision=less uncertainty about the target parameter

Question 17

Sampling distribution

Answer 17

probability distribution of values for an estimate obtained from sampling the population

Question 18

Frequency distribution

Answer 18

describe the number of time each value of a variable occurs in a sample can use absolute (numbers) or relative (proportions) values

Question 19

Population

Answer 19

the set of all subjects relevant to the scientific hypothesis under examination

Question 20

Census

Answer 20

a collection of data where the entire population is examined

Question 21

Non random sampling

Answer 21

pick the sample based on a certain characteristic

Question 22

Experimental study

Answer 22

(random assignment ensures causality and remove bias)/ provide higher standard of evidence, because researchers assign or impose conditions randomly rather than relying on comparisons of existing conditions

Question 23

Observational study

Answer 23

record variables measuring patient health and compare groups A and B

Question 24

is experimental better or observational?

Answer 24

experimental are better because they provide higher standard of evidence because researchers assign or impose conditions randomly rather than relying on comparison of existing conditions

Question 25

what are the types of variables?

Answer 25

Quantitative (numerical) Qualitative (categorical)

Question 26

Quantitative variables

Answer 26

Continuous ( measured/ can have any value), could be any value/rate, area, height Discrete ( Counted/ Indivisible),number of siblings, counts Interval: meaningful zero (temp, altitude and longitude) (mostly continuous), zero doesn't mean nothing, it has a meaning Ratio: zero=nothing (you can have zero offspring meaning you have no offspring)

Question 27

Qualitative variables

Answer 27

Nominal ( no order) colour of shirt/ yes, no Ordinal (ordered) letter grade/ pass, fail

Question 28

Explanatory variable (independent)

Answer 28

responsible for the change in the response variable

Question 29

Response variable (dependent)

Answer 29

focus of the study could be: frequency, the count of observations in each bin proportion, of the total observations in each bin density, the proportion of the total observations per unit of the bin width(area under the curve)

Question 30

how do we illustrate Frequency distributions?

Answer 30

for categorical or discrete data=bar graph for continuous data= historgram

Question 31

differences among distributions in histograms could be due to:

Answer 31

1.different location or central tendency 2.different spread or scale measured using std 3.distributions with a different shape or skew

Question 32

what are the measures of location in histograms?

Answer 32

central tendency: 1. mean: arithmetic average 2.median: middle of the data 3.mode: most commonly occurring observation

Question 33

measure of scale?

Answer 33

range, variance, standard deviation(best since it has same units as original variables)

Question 34

Residuals

Answer 34

The difference between an observation and mean -sufficiently large sample from a normal distribution will have residuals that are normally distributed and entered on zero

Question 35

measure of shape

Answer 35

measure the asymmetry: left skewed right skewed

Question 36

confidence interval

Answer 36

range of values that is likely to contain the true population parameter (mean- 2x standard error) when it normally distributed, a 95% interval is a range of values, calculated from sample data, that would contain the true population parameter in 95 out of 100 samples if the sampling process were repeated