Notes, summaries, assignments, exams, and problems for Mathematics

Chapter 1: Understanding Variables

Types of Variables

• Categorical: Smoker (current, former, no)
• Ordinal: Non, light, moderate, heavy smoker (ordered categories)
• Quantitative: BMI, Age, Weight (numerical measurements)

Key Definitions

• Observation: Measurements are made (individual or aggregate).
• Variable: The generic characteristic we measure (e.g., age).
• Value: A realized measurement (e.g., 27).

Chapter 2: Statistical Studies

Surveys: Census and Sampling

• Goal: Describe population characteristics.
• Census: Attempts to reach the entire population (costly, time-consuming).
• Sampling: Uses a sample of the population (allows for inferences, saves time and money).
• Simple Random Sampling: Based on probability.
• Issues with Sampling: Under-coverage, volunteer bias,

Investment Portfolio and CAPM Practice Solutions

• Question 1: Portfolio beta (0.6)
• Question 2: Expected return under CAPM (7%)
• Question 3: Expected return with new allocation (6.5%)
• Question 4: Passive investment strategy (Zero alpha)
• Question 5: Net Asset Value calculation ($50)
• Question 6: Definition of NAV (Market value of assets minus liabilities divided by shares outstanding)
• Question 7: Portion of market risk (64%)
• Question 8: Mutual fund return after expenses (4.5%)
• Question 9: Net Asset Value City Street Fund ($40)
• Question 10: Impact on portfolio value (Decreases to $460 million)
• Question 11: Impact on shares outstanding (Decreases to 9 million)
• Question 12: New NAV after shares sold ($40)
• Question 13: Risk premium for stocks (60%)
• Question 14: Optimal

Common Statistical Biases

• Sampling bias: The sample was not representative of the population.
• Non-response bias: Only 24% returned surveys.

Sampling Techniques

• Simple Random Sampling (SRS): 1) Every member of the population has the same chance of being included (representative). 2) Members are chosen independently.
• Random Cluster Sampling: 1) Divide into smaller geographical sectors. 2) Take an SRS of sectors. 3) Count all samples in sectors and scale appropriately.
• Stratified Random Sampling: 1) Divide population into groups based on criteria like age or income. 2) Perform an SRS of each group and scale appropriately.

Data Variables and Distributions

• Variable Types: Categorical and Numeric (discrete and continuous).
• Relative frequency: Count / sample

Algebra and Trigonometry Problem Set

1. y = -6x³ + 4x² - x + 2
2. Vertical shrink by 1/2, horizontal translation 2 to the left, vertical translation 1 down
3. 4x⁴ - 11x³ + 7x² + 5x - 3
4. $713,476.20
5. Brian is designing a handrail for a staircase and needs to determine the length: 12
6. A meteorologist predicts a 42% chance of rain on Saturday and a 54% chance of rain on Sunday: 27%
7. a_n = 3n - 11
8. (-2, 6) lies on the terminal side of an angle θ in standard position: Sinθ = 3√10 is False, True, True
9. y = log(x - 2)
10. Find the sum of the series: 12
11. The table shows enrollment by gender as an undergraduate or graduate student: 515/2463 = 0.209

Zeros of Functions

12. Find the zeros of the function shown below:
f(x) = x² + 3x - 10: x = 2 and -5

Statistical Distributions

13. Normal... Continue reading "Algebra and Trigonometry Practice Problem Solutions" »

Set Difference Calculation

To find the set difference A - B, we identify all elements present in set A but not in set B.

Step-by-Step Subtraction

• Is 1 ∈ B? No. (Keep 1)
• Is 2 ∈ B? No. (Keep 2)
• Is 3 ∈ B? Yes. (Remove 3)
• Is 5 ∈ B? No. (Keep 5)
• Is 7 ∈ B? Yes. (Remove 7)
• Is 8 ∈ B? No. (Keep 8)

The remaining elements from set A are {1, 2, 5, 8}.

Symbolic Logic

In symbolic logic, the word "but" functions like "and," indicating that both conditions occur simultaneously. To write "He is rich but not generous" in symbolic form:

• p: "He is rich"
• q: "He is generous"
• ¬q: "He is not generous"
• ∧: The conjunction operator

Logic Symbol Reference

Logarithm Calculations

To find the value of log 360,... Continue reading "Step-by-Step Solutions for Mathematical Problems" »

Parametric Inference Fundamentals

The probability distribution of the population under study is known, except for a finite number of parameters. Its goal is to estimate those parameters. Examples include the T-test and ANOVA.

Non-Parametric Inference Basics

The distribution of the population is not known. It is used to test the assumptions of parametric methods, for example, to check if the population distribution is normal.

What is a Statistic?

A random variable function of the sample that does not depend on the unknown parameter.

Understanding Estimators

A statistic whose values are acceptable for estimating an unknown parameter.

Unbiasedness in Estimation

We do not allow systematic overestimation or underestimation of the parameter, which would result... Continue reading "Statistical Inference & Hypothesis Testing Concepts" »

De Morgan's Law

De Morgan's Law: (Flip if the union is true)

, image of set: [min, max]; one-to-one: horizontal line test; Onto: Image must equal domain; Bijective: one-to-one and Onto

|| EV

||

Possible Outcomes and Probability Calculations

• Repetition formula: n^k
  • Example: 5 awards (k) and 30 students (n), with no limit to awards per student.
• Permutation formula: P(n, k) = n! / (n - k)!
  • Example: Each student gets 1 award, so the number of students decreases by one each award.
• No overlap probability: P(n, k) / repetition formula
• Arrangements: a = slots → a! can be multiplied by arrangements within slots
• Die sum probability:
  • List combinations that lead to the sum for each die.
  • If a die is rolled multiple times, each combination has (rolls)! permutations.
  • Add

Probability Distributions for Discrete Events

The following table matches common scenarios to their appropriate probability distributions:

Bar Graph: Annual Sales of Product A and B

The bar chart illustrates the annual dollar sales of Product A and Product B for the years 2015, 2016, and 2017. As can be seen in the graph, between 2015 and 2017 sales of Product A were higher than sales of Product B. In 2015, sales of Product B were slightly lower than Product A, and in 2016 sales of Product A reached 80,000 USD while sales of Product B only reached 50,000 USD. For 2017, both Product A and Product B had a slight growth, increasing their sales by 10,000 USD compared to the previous year. Overall, we can see that sales of both products have grown in the last three years; however, the product that generates the most revenue is Product A.

Line Chart: Six-Year Sales Trend

The graph shows... Continue reading "Annual Sales Trends and Household Water Usage Data" »