Data Science Notes

Question 1

What is a python list ?

Answer 1

A python list is a sequence of values. It can consist of any types of data.
Lists are mutable meaning that you can change the order of item and reassign a new item.

Question 2

What is NumPy ?

Answer 2

Numpy provides the ndarray object for efficient storage and manipulation of dense data arrays in python.

Question 3

What is Pandas ?

Answer 3

• This library provides the DataFrame object for efficient storage and manipulation of labeled/columnar data in python.
• Pandas is high level tool for doing data manipulation/transformation

Question 4

What is a distribution?

Answer 4

distribution is the set of all possible random variables together. a random variable is the result of each flip of a coin.

Question 5

What is a binomial distribution?

Answer 5

the distribution is called binomial since there are two possible outputs a heads or a tails.

Question 6

What is discreet distribution?

Answer 6

There are only categories being used a heads and a tails and not real numbers.

Question 7

What is broadcasting?

Answer 7

Broadcasting is simply a set of rules for applying binary ufuncs (addition, subtraction etc.) on arrays of different sizes.

for example: [1, 2, 3] + 5 = [6, 7, 8]

Question 8

What are the rules of broadcasting?

Answer 8

1. If array shapes differ, left-pad the smaller shape with 1s
2. If any dimensions does not match, broadcast the dimensions with size = 1
3. If neither non-matching dimension is 1, raise an error.

Question 9

What is fancy indexing?

Answer 9

it means passing an array of indices to access multiple array elements at once.

Question 10

What is central tendency?

Answer 10

Central tendency refers to the central position of the data (mean, median, mode) while the deviation describes how far spread out the data are from the mean.

Question 11

What is deviation?

Answer 11

Deviation is most commonly measured with the standard deviation. A small standard deviation indicates the data are close to the mean, while a large standard deviation indicates that the data are more spread out from the mean.

Question 12

What is Descriptive statistics?

Answer 12

Descriptive statistics identify patterns in the data, but they don’t allow for making hypotheses about the data.

Question 13

What is Inferential statistics?

Answer 13

Inferential statistics allow us to make hypotheses (or inferences) about a sample that can be applied to the population.

Question 14

What is correlation matrix with pandas’ corr method. ?

Answer 14

The values in the correlation matrix table will be between -1 and 1. A value of -1 indicates the strongest possible negative correlation, meaning as one variable decreases the other increases. And a value of 1 indicates the opposite.

Question 15

Descriptive Statistics

Answer 15

Descriptive statistics are a collection of statistical tools which are used to quantitatively describe or summarize a collection of data. Descriptive statistics aim to summarize, and as such can be distinguished from inferential statistics, which are more predictive in nature.

Question 16

Population

Answer 16

A population is a selected individual or group representing the full set of members of a certain group of interest.

Question 17

Sample

Answer 17

A sample is a subset drawn from a larger population. If this drawing is accomplished in such a manner that each member of the population has an equitable chance of selection, the result is referred to as a random sample.

Question 18

Statistic

Answer 18

A statistic is a value which is generated from a sample. If I calculated the mean age of a subset of humans on planet Earth (much more feasible), this value would be a statistic. Hence, the discipline of statistics.

Question 19

Generalizability

Answer 19

Generalizability refers to the ability to draw conclusions about the characteristics of the population as a whole based on the results of data collected from a sample. This is ability is not a given, and depends heavily on the nature of sample collection, sample size, and various other factors.

Question 20

Distribution

Answer 20

A distribution is the arrangement of data by the values of one variable in order, from low to high. This arrangement, and its characteristics such as shape and spread, provide information about the underlying sample.

Question 21

Mean

Answer 21

Mean, along with median and mode, is one of the 3 major measures of central tendency, which collectively evaluate an important and basic aspect of a distribution. The simple arithmetic average of a distribution of variable values (or scores), the mean provides a single, concise numerical summary of a distribution. The mean is also likely the most common statistics encountered in general research. Population mean is denoted μ, while sample mean is denoted x̄.

Question 22

Median

Answer 22

The median is the score of a distribution residing at the 50th percentile, separating the top and bottom 50 percent of scores. The median is useful for both splitting a set of distribution scores in half and helping to identify the skew of a distribution.

Question 23

Mode

Answer 23

The mode is simply the score which appears most frequently in the distribution. Multimodal refers to a distribution with more than one mode; bimodal refers to a distribution with 2 modes.

Question 24

Skew

Answer 24

When there are more scores toward one end of the distribution than the other, this results in skew. When the scores of a distribution are more clustered at the high end, the relatively fewer number of scores on the low end result in a tail, with the scenario being referred to as negative skew. Positive skew is when a distribution shows a tail at its high end.

In general, in a negatively skewed distribution, we would expect the mean to be less than the median, while in a positively skewed distribution, we would expect the mean to be greater than the median.

Question 25

Range

Answer 25

One of the most important measures of dispersion, the range is the difference between the maximum and minimum values of a distribution.

Question 26

Variance

Answer 26

Variance is the statistical average of the dispersion of scores in a distribution. Variance is not often used on its own, but can be a useful calculation on the way to a more descriptive statistical measurement, such as standard deviation.

Question 27

Standard Deviation

Answer 27

The standard deviation of a distribution is the average deviation between individual distribution scores and the distribution’s mean. Individually, the standard deviation provides a good measure of how spread out a disquisitions scores are. When considered alongside the mean, these 2 measures provides a good overview of the distribution of scores.

Question 28

Interquartile Range (IQR)

Answer 28

The IQR is the difference between the score delineating the 75th percentile and the 25th percentile, the third and first quartiles, respectively.