Definitions of Statistics, Probability, and Key Terms Statistics

I calculated the Expected Value of each channel by multiplying the probability of success (conversion rate) with the payoff (average revenue per conversion). For instance, if Channel A had a conversion rate of 0.2 and an average revenue of $500 per conversion, its Expected Value was $100. Variance, on the other hand, measures how spread out these values are around the expected value. A high variance indicates that the data points are far from the mean and each other, implying more unpredictability or risk. Conversely, a low variance suggests that the values tend to be close to the mean and to each other, indicating less variability or risk. This query multiplies each probability by its corresponding outcome and then sums up these products to give the expected value.

  1. For some probability distributions, there are short-cut formulas for calculating μ and σ.
  2. It’s an objective measure based on long-term frequency of occurrence.
  3. In order to find the probability of winning, I need to figure out all possible lottery outcomes.
  4. All that can be said is that one person is higher or lower on the scale than another, but more precise comparisons cannot be made.
  5. Another approach could be using stochastic models such as Monte Carlo simulations.

Through these questions, we aim to deepen your understanding of Expected Value and its applications across various domains. The average length of time (in months) AIDS patients from the sample live after treatment. Variance
Similarly, when looking at quantities in the interest of variance as the model distribution there is also an unbiased estimator that should satisfy the two equations below.


The company selects
500 doctors at random from a professional directory and determines the number in
the sample who have been involved in a malpractice lawsuit. A random variable is a variable whose distribution function assigns values to different outcomes of an experiment. They are classified as discrete, which have specific values with finite or infinite ranges, or continuous, which can take any value in some interval on the real number line. In the lottery case, drawing a number from 49 numbers can only have integer numbers in the range [1,49]. Therefore, I am working with a discrete random variable in the lottery context.


If we let [latex]Y[/latex] be a person’s party affiliation, then some examples of [latex]Y[/latex] include Republican, Democrat, and Independent. Because it takes a lot of time and money to examine an entire population, sampling is a very practical technique. If you wished to compute the overall grade point average at your school, it would make sense to select a sample of students who attend the school. The data collected from the sample would be the students’ grade point averages.

To calculate the expected value of a discrete random variable in Python, you would first need to define your probability mass function (PMF). This is typically done by creating a dictionary where keys represent possible outcomes and values represent their corresponding probabilities. Expected value, a fundamental concept in statistics and probability theory, is the long-run average value of repetitions of the same experiment it represents.

The parameter is the average (mean) amount of money spent (excluding books) by first year college students at ABC College this term. If you flip a coin two times, does probability tell you that these flips will result in one heads and one tail? As you learned in [link], probability does not describe the short-term results of an experiment.

For each value x, multiply the square of its deviation by its probability. To find the expected value or long term average, μ, simply multiply each value of the random variable by its probability and add the products. One of the most common uses of the word “average” is what mathematicians and statisticians call the arithmetic mean, or just plain old mean which among the central tendency measurements is used best for the variable “lottery ticket”? for short. “Arithmetic mean” sounds rather fancy, but you have likely calculated a mean many times without realizing it; the mean is what most people think of when they use the word “average”. Cars with dummies in the front seats were crashed into a wall at a speed of 35 miles per hour. The questions above ask you to analyze and interpret your data.

A variable, or random variable, usually notated by capital letters such as X and Y, is a characteristic or measurement that can be determined for each member of a population. Numerical variables take on values with equal units such as weight in pounds and time in hours. Categorical variables place the person or thing into a category.

1 Definitions of Statistics, Probability, and Key Terms

Complete the following table to find the mean and standard deviation of X. A venture capitalist, willing to invest 💲1,000,000, has three investments to choose from. The first investment, a software company, has a 10% chance of returning 💲5,000,000 profit, a 30% chance of returning 💲1,000,000 profit, and a 60% chance of losing the million dollars. The second company, a hardware company, has a 20% chance of returning 💲3,000,000 profit, a 40% chance of returning 💲1,000,000 profit, and a 40% chance of losing the million dollars. The third company, a biotech firm, has a 10% chance of returning 💲6,000,000 profit, a 70% of no profit or loss, and a 20% chance of losing the million dollars.

Introductory Statistics

To calculate the standard deviation (σ) of a probability distribution, find each deviation from its expected value, square it, multiply it by its probability, add the products, and take the square root. To understand how to do the calculation, look at the table for the number of days per week a men’s soccer team plays soccer. To find the standard deviation, add the entries in the column labeled (x – μ)2P(x) and take the square root. Expected Value (EV) is a statistical concept used in optimization problems to predict the average outcome over numerous trials. It’s calculated by multiplying each possible outcome by its probability and summing these products. In an optimization problem, EV can be applied to determine the best decision among several options.

Introduction to Statistics

Three of those students spent 150, 200, and 225, respectively. In this course, you will learn how to organize and summarize data. Organizing and summarizing data is called descriptive statistics. Two ways to summarize data are by graphing and by using numbers (for example, finding an average).

The sample mean is used as the ‘best guess’ approximation of the population mean. The sample is the 75 cars, selected by a simple random sample. The population is all first year students attending ABC College this term.

Leave a Comment