economic methods statistics

Question 1

what is data?

Answer 1

it is a body of numerical evidence

Question 2

what is population?

Answer 2

a population is the collection of all items under investigation

Question 3

what is a sample?

Answer 3

a sample is an observed subset of the population.

Question 4

what is a parameter?

Answer 4

a parameter is a specific characteristic of population

Question 5

what is a statistic?

Answer 5

it is a specific characteristic of a sample

Question 6

what are the two branches of statistics?

Answer 6

descriptive statistics and inferential statistics

Question 7

what is a descriptive statistic?

Answer 7

graphical and numerical procedures to summarise and process data

Question 8

what is inferential statistics ?

Answer 8

the use of sample data to make predictions and estimates about the population

Question 9

what are the two types studies ?

Answer 9

observational and experimental

Question 10

what is an observational study?

Answer 10

the observational study does not directly interfere with how data arise. it could be retrospective or prospective

Question 11

what is an experimental study?

Answer 11

an experimental study randomly assign subjects to treatment. it directly involves with how data arises.

Question 12

what is a simple random sample?

Answer 12

a simple random sample is a procedure in which:
- each member of the population is chosen strictly by chance
- each member of the population is equally likely to be chosen
- every possible sample of objects is equally likely to be chosen

Question 13

what is needed for observational data to be reliable?

Answer 13

If observational data are not collected in a random framework from a population, these statistical methods – the estimates and errors associated with the estimates – are not reliable.

Question 14

what is systematic sampling?

Answer 14

Suppose that the population list is arranged in some fashion unconnected with the subject of interest. Systematic sampling involves the selection of every j th item in the population, where j is the ratio of the population size N to the desired sample size, n ; that is, j = N > n . Randomly select a number from 1 to j to obtain the first item to be included in your systematic sample.

Question 15

what is a histogram?

Answer 15

it is a graph that provides a view of data distribution among a population. the higher the bars represnt where data is more common. on the Y axis is frequency density and on x are the bins. a chosen bin width can alter the story the histogram is telling.

Question 16

what does unimodal mean?

Answer 16

a single peak

Question 17

what does bi modal mean

Answer 17

two peaks

Question 18

what does multimodal mean

Answer 18

more than two peaks

Question 19

what does uniform histogram mean

Answer 19

rougly straight line across the bars. it can have some peaks but they need to be close together

Question 20

what are the two ways of describing data numerically

Answer 20

central tendency and variation

Question 21

what does central tendency include?

Answer 21

mean, median and the mode

Question 22

what does variation include?

Answer 22

range , interquartile range, variance, standard deviation, coefficient of variation

Question 23

what is the mean

Answer 23

the average of the data. it comes in two forms sample and population

Question 24

what is the formula for the sample mean?

Answer 24

x1+x2+x3….xn/n where n is sample size

Question 25

what is the formula for the population mean?

Answer 25

population mean is equal to x1 +x2+x3...xN/ N where N is population size

Question 26

what is the median?

Answer 26

the middle point value of an ordered list

Question 27

what is the mode?

Answer 27

the mode is the most frequently observed value

Question 28

what is a flaw with the mode?

Answer 28

it may not exist or there may be multiple

Question 29

what is a benefit of the mode

Answer 29

it is not affected by outliers

Question 30

what is a benefit with the median?

Answer 30

it is not affected by outliers

Question 31

what is the formula for finding the median?

Answer 31

The location of the median is found by the formula (n+1)/2 , if number is odd it will give you a number in list but if number of observations is even then the median is the mean of two numbers . the value outputted by the formula is not the median value but instead the point in list where the median will be found

Question 32

what is a flaw with the mean?

Answer 32

it is affected by outliers

Question 33

what are the three ways a data can be distributed?

Answer 33

it can be symetric, left skewed or right skewed

Question 34

when is a curve left skewed?

Answer 34

A curve is left skewed when the mean < median

Question 35

when is a curve right skewed?

Answer 35

A curve is right skewed when the mean> median

Question 36

when is a curve symmetric?

Answer 36

A curve is symetric when the median is equal to the mean

Question 37

what is a percentile?

Answer 37

A percentile indicates the value below which a given percentage of observations lie

Question 38

what is a quartile?

Answer 38

Quartiles split the ranked data into 4 segments with an equal number of values per segment( although the widths may vary)

Question 39

what is the five number summary and what does it include?

Answer 39

Refers to the descriptive measures Minimum First quartile Median Third quartile Maximum

Question 40

what is the measures of variability?

Answer 40

the Measures of variability gives information on the spread of variability

Question 41

what are the different types of measurements of variablity?

Answer 41

Range, interquartile range, variance, standard deviation, coefficient of variation

Question 42

what is the range?

Answer 42

The simplest measure of variation The difference between the largest value and the smallest observation

Question 43

what is the flaw with using the range?

Answer 43

it is affected by outliers

Question 44

what is the interquartile range?

Answer 44

The difference between the difference between the observation at the third quartile and the observation at the first quartile

Question 45

what is the benefit of using the interquartile range?

Answer 45

it is not as affected by outliers

Question 46

what is the flaw with using the interquartile range?

Answer 46

it does not take into account the full population which might not be representative of the total population/

Question 47

what is the population varience?

Answer 47

The population varience is the mean of the squared deviations of values from the mean

Question 48

why do you square the numbers in the varience?

Answer 48

the calculation of variance uses squares because it weighs outliers more heavily than data that appears closer to the mean. This calculation also prevents differences above the mean from canceling out those below, which would result in a variance of zero.

Question 49

what is the formula for the varience

Answer 49

mean of the squares minus the square of the means

Question 50

what is the sample varience?

Answer 50

The sample varience is the mean (approximately) of the squared deviations from the mean

Question 51

what is the standard deviaton?

Answer 51

it is the most commonly used measure of variation. it is the square root of the variance

Question 52

what is the advantage of using the standard deviation over varience?

Answer 52

Its advantage over variance is that it has the same units as the original data

Question 53

what is the coefficent of variation?

Answer 53

Measures the relative variation Is expressed as a percentage Can be used to compare two or more sets of data measured in different units There is a population coefficient of variation, there is also a sample coefficient of variation

Question 54

what are the 2 measures of relationships between variables?

Answer 54

there is the covarience and the correlation coefficient

Question 55

what is the correlation coefficient?

Answer 55

Correlation coefficent- a measure of both the direction and strength of a linear relationship between two variables

Question 56

what is the covariance?

Answer 56

Covariance- a measure of the direction of a linear relationship between two variables

Question 57

what do the variables do when the covariance is positive (negative)?

Answer 57

When the covariance is positve (negative) the variables tend to move in the same(opposite) direction

Question 58

what is the correlation when the coefficent is closer to 1 or (-1)?

Answer 58

The closer the correlation coefficient is to 1 ( -1), the stronger is the postive (negative ) linear relationship between the variables