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economic methods > economic methods statistics > Flashcards

economic methods statistics Flashcards

1
Q

what is data?

A

it is a body of numerical evidence

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2
Q

what is population?

A

a population is the collection of all items under investigation

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3
Q

what is a sample?

A

a sample is an observed subset of the population.

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4
Q

what is a parameter?

A

a parameter is a specific characteristic of population

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5
Q

what is a statistic?

A

it is a specific characteristic of a sample

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6
Q

what are the two branches of statistics?

A

descriptive statistics and inferential statistics

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7
Q

what is a descriptive statistic?

A

graphical and numerical procedures to summarise and process data

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8
Q

what is inferential statistics ?

A

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

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9
Q

what are the two types studies ?

A

observational and experimental

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10
Q

what is an observational study?

A

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

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11
Q

what is an experimental study?

A

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

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12
Q

what is a simple random sample?

A

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

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13
Q

what is needed for observational data to be reliable?

A

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.

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14
Q

what is systematic sampling?

A

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.

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15
Q

what is a histogram?

A

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.

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16
Q

what does unimodal mean?

A

a single peak

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17
Q

what does bi modal mean

A

two peaks

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18
Q

what does multimodal mean

A

more than two peaks

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19
Q

what does uniform histogram mean

A

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

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20
Q

what are the two ways of describing data numerically

A

central tendency and variation

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21
Q

what does central tendency include?

A

mean, median and the mode

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22
Q

what does variation include?

A

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

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23
Q

what is the mean

A

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

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24
Q

what is the formula for the sample mean?

A

x1+x2+x3….xn/n where n is sample size

25
Q

what is the formula for the population mean?

A

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

26
Q

what is the median?

A

the middle point value of an ordered list

27
Q

what is the mode?

A

the mode is the most frequently observed value

28
Q

what is a flaw with the mode?

A

it may not exist or there may be multiple

29
Q

what is a benefit of the mode

A

it is not affected by outliers

30
Q

what is a benefit with the median?

A

it is not affected by outliers

31
Q

what is the formula for finding the median?

A

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

32
Q

what is a flaw with the mean?

A

it is affected by outliers

33
Q

what are the three ways a data can be distributed?

A

it can be symetric, left skewed or right skewed

34
Q

when is a curve left skewed?

A

A curve is left skewed when the mean < median

35
Q

when is a curve right skewed?

A

A curve is right skewed when the mean> median

36
Q

when is a curve symmetric?

A

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

37
Q

what is a percentile?

A

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

38
Q

what is a quartile?

A

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

39
Q

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

A

Refers to the descriptive measures

Minimum

First quartile

Median

Third quartile

Maximum

40
Q

what is the measures of variability?

A

the Measures of variability gives information on the spread of variability

41
Q

what are the different types of measurements of variablity?

A

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

42
Q

what is the range?

A

The simplest measure of variation

The difference between the largest value and the smallest observation

43
Q

what is the flaw with using the range?

A

it is affected by outliers

44
Q

what is the interquartile range?

A

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

45
Q

what is the benefit of using the interquartile range?

A

it is not as affected by outliers

46
Q

what is the flaw with using the interquartile range?

A

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

47
Q

what is the population varience?

A

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

48
Q

why do you square the numbers in the varience?

A

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.

49
Q

what is the formula for the varience

A

mean of the squares minus the square of the means

50
Q

what is the sample varience?

A

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

51
Q

what is the standard deviaton?

A

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

52
Q

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

A

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

53
Q

what is the coefficent of variation?

A

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

54
Q

what are the 2 measures of relationships between variables?

A

there is the covarience and the correlation coefficient

55
Q

what is the correlation coefficient?

A

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

56
Q

what is the covariance?

A

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

57
Q

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

A

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

58
Q

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

A

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

economic methods (7 decks)

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