Statistics for Economists Lecture Notes Flashcards

Flashcards covering introductory statistics, variables, measurement scales, descriptive and inferential methods, probability distributions, estimation, and linear regression based on the March 2026 lecture notes by Emmanuel Lawluvi.

Statistics

The scientific discipline that provides methods for organizing and summarizing data and for drawing conclusions based on information contained in the data.

Descriptive Statistics

The branch of statistics that deals with describing data in the form of tables, graphs, or summary measures.

Inferential Statistics

The process of making decisions and drawing reliable conclusions about a population based upon a sample drawn from the population.

Variable

Any measurable characteristic of an element that can assume different values, such as marital status or annual income.

Bivariate Data Set

A collection of observations made on exactly two variables for each element in a study.

Element

The entities on which data are collected; they can be persons, companies, items, or countries.

Census

A data collection process that involves the entire population.

Statistic

A numerical measure that describes a specific characteristic of a sample.

Parameter

A numerical measure that describes a specific characteristic of a population.

Sampling Error

The difference between a sample statistic and its corresponding population parameter.

Qualitative Variables

Categorical variables with values that can only be placed into categories, such as gender or blood group.

Discrete Quantitative Variables

Variables consisting of observations that can be counted and have integer values, with no intermediate values between consecutive numbers.

Continuous Quantitative Variables

Variables that can take on any numerical value within a specific range and typically result from measuring.

Nominal Level

The lowest level of measurement, used only to name, categorize, or classify variables using numbers or letters as markers.

Ordinal Level

A measurement scale that classifies data into distinct categories where ranking is implied, but the magnitude of differences between categories is unknown.

Interval Level

A measurement scale where differences between measurements are meaningful, but there is no true zero point indicating the absence of the attribute.

Ratio Level

The highest level of measurement, where differences are meaningful and a true zero point exists, allowing multiples to be meaningful.

Time Series Data

Data values for the same variable on the same element recorded at different regular intervals over time.

Cross-sectional Data

Data collected on different individual entities (such as households or firms) at a single point in time.

Pooled (Panel) Data

A data set consisting of data collected on different elements at multiple time intervals.

Primary Data

Data generated by the researcher for a specific purpose or decision using tools like questionnaires, interviews, or observations.

Simple Random Sampling

A sampling method where every element of the population has an equal chance of being selected.

Systematic Random Sampling

A method where elements are selected at regular intervals, specifically every $k^{th}$ case after a random start.

Stratified Random Sampling

A sampling method where the population is divided into mutually exclusive groups called strata, and a random sample is taken from each group.

Cluster Sampling

A method where the population is divided into groups called clusters, some of which are randomly selected for full membership inclusion in the sample.

Frequency Distribution

A table that displays the counts of items in each non-overlapping class of a particular variable within a data set.

Relative Frequency

The proportion of total frequencies falling into a given class, calculated as $\frac{\text{frequency of that class}}{\text{sum of all frequencies}}$.

Pareto Diagram

A variation of a bar chart where categories are ordered from the largest frequency on the far left to the smallest on the right.

Cumulative Frequency

A running total of frequencies through class intervals.

Lorenz Curve

A specialized graphical presentation used to indicate the disparity between the values of variables by comparing them to a line of equal distribution.

Arithmetic Mean

A measure of central tendency obtained by adding all observations and dividing by the count ($\mu = \frac{\sum x_i}{N}$ or $\bar{x} = \frac{\sum x_i}{n}$).

Weighted Mean

A mean computed by giving each observation a weight reflecting its relative importance, calculated as $\bar{x}_w = \frac{\sum w_i x_i}{\sum w_i}$.

Median

The middle value of a ranked data set where half the observations are smaller and half are larger.

Mode

The observation in a data set that occurs more than once and most often.

Standard Deviation

A measure describing the extent to which data values deviate from the mean, calculated as the square root of the variance ($\sigma = \sqrt{\sigma^2}$).

Coefficient of Variation

A relative measure used to compare the variations in two or more data sets with different units, expressed as $\text{CV} = \frac{\sigma}{\mu} \times 100\%$.

z-score

A measure of a data value in terms of the number of standard deviations it is from the mean ($z = \frac{x - \mu}{\sigma}$).

Quartiles

Summary measures that split an ordered data set into four equal parts.

Interquartile Range (IQR)

A measure of variability resistant to outliers, defined as the difference between the third and first quartiles ($Q_3 - Q_1$).

Skewness

A measure reflecting a data set in which values are heavily condensed in one range and less condensed in another.

Sample Space (\Omega)

The set of all distinct possible outcomes of a random experiment.

Mutually Exclusive Events

Two events that have no outcomes in common and whose intersection is an empty set.

Bayes' Theorem Requirement (Conditional Probability)

The likelihood an event occurs given that another related event has already occurred, denoted as $\text{Pr}(E_1|E_2)$.

Binomial Distribution

A discrete probability distribution used for a fixed number of independent trials with only two possible outcomes (success or failure).

Poisson Distribution

A probability distribution describing the number of events occurring in a specific time or space if events happen with a known average rate ($\lambda$).

Normal Distribution

A bell-shaped, symmetric, continuous probability distribution determined by its mean ($\mu$) and standard deviation ($\sigma$).

Point Estimate

The value of a population parameter given by a single number derived from a sample statistic.

Confidence Interval

A range of reasonable values in which a population parameter is expected to fall with a chosen degree of certainty.

Type I Error

An error in hypothesis testing that occurs when a true null hypothesis is rejected.

Type II Error

An error in hypothesis testing that occurs when one fails to reject a false null hypothesis.

Significance Level (\alpha)

The probability of making a Type I error.

Regression Analysis

A statistical technique for investigating and modeling the relationship between a dependent variable and one or more independent variables.

Coefficient of Determination (R^2)

The proportion of the total variation in the dependent variable explained by the variation in the independent variable(s).