Intro to Linear Regression

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Questions and Answers

Which type of question does regression analysis primarily address?

  • Forecasting 'how much' (correct)
  • Grouping similar data points
  • Determining category membership
  • Identifying causal relationships

In linear regression, the goal is to fit a curve, rather than a straight line, through the data points.

False (B)

In the context of predicting house prices using linear regression, what does the 'fitting' process refer to?

drawing a line through the dataset

In linear regression for predicting house prices, what does the x-axis commonly represent?

<p>Size of the house (A)</p>
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Increasing the slope (w₁) in the equation $y = w_1x + w_2$ while keeping $w_2$ constant will make the line steeper.

<p>True (A)</p>
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In the linear equation $y = w_1x + w_2$, the term w_2 represents the ________.

<p>y-intercept</p>
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Match the terms with their descriptions in the context of linear regression:

<p>Independent variable = Variable used to predict the other variable's value Dependent variable = Variable whose value is being predicted Slope = Rate of change of the dependent variable with respect to the independent variable Y-intercept = Point where the regression line crosses the y-axis</p>
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What is the primary goal of linear regression?

<p>To find the 'best-fit' line that minimizes the difference between predicted and actual values (B)</p>
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Batch gradient descent updates the weights of the model after processing each individual data point.

<p>False (B)</p>
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Explain the difference between stochastic gradient descent and batch gradient descent in linear regression.

<p>stochastic updates weights after each point, batch after all points</p>
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Which of the following is an example of a regression task?

<p>Predicting the price of a house (A)</p>
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In linear regression, the predicted output must be a continuous value.

<p>True (A)</p>
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In linear regression, the variable that is being predicted is known as the ________ variable.

<p>dependent</p>
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If you are building a linear regression model to predict the selling price of a house based on its size, what represents the independent variable?

<p>The size of the house (D)</p>
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The goal in linear regression is to minimize the sum of the errors, so it doesn't matter if some errors are positive and some are negative.

<p>False (B)</p>
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Why is it generally better to use Mean Squared Error (MSE) than simply summing the errors in linear regression?

<p>MSE avoids cancellation of positive and negative errors</p>
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If you want to compare the errors of batches with different sizes in stochastic gradient descent, what should you do?

<p>Normalize the errors by taking the average (D)</p>
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In the equation $y = 5x + 100$ that predicts house prices, the number 5 represents the y-intercept.

<p>False (B)</p>
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The equation $y = w_1x_1 + w_2x_2+...+w_nx_n+b$ represents a ________ in linear regression where multiple features/inputs are considered.

<p>prediction</p>
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What is Fitting Line using gradient descent (MSE)?

<p>Training (C)</p>
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If the size of the house is the x-axis & the price of the house is the y-axis, then which of the following is the best explanation?

<p>The y-axis represents the price of the house in Dollars and the x-axis represents the size of the house. (C)</p>
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When is Polynomial Regression used?

<p>For non-linear dataset (B)</p>
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What type of machine learning algorithm is Logistic regression?

<p>Supervised Machine Learning (C)</p>
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The goal of Logistical Regression is generally classifying emails as spam vs not spam.

<p>True (A)</p>
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_________ is used to map the predicted values to probabilities.

<p>sigmoid function</p>
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What does 'e' stand for in this equation: $f(x) = \frac{1}{1+e^{-(x)}}$?

<p>Number of Euler (C)</p>
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The equation $f(x) = \frac{1}{1+e^{-(x)}}$ is Linear Regression.

<p>False (B)</p>
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The y-intercept is also known as w[number]?

<p>2</p>
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Given the equation $y = w_1x + w_2$, which variable is best described as the Slope?

<p>$w_1$ (D)</p>
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Regression always answers a classification question.

<p>False (B)</p>
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________ Gradient Descent applies the squared (or absolute) trick at every point in our data one by one, and repeating this process many times.

<p>stochastic</p>
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What is considered the Independent Variable, when trying to predict the size of a house?

<p>Price (C)</p>
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Linear Regression does not fall under Supervised Learning.

<p>False (B)</p>
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Trying to predict the price of a house given its size is an example of which task?

<p>regression</p>
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In the equations given earlier: $y = w_1x + w_2$ & $y = w_1x_1 + w_2x_2+...+w_nx_n+b$, what does $x$ stand for?

<p>Independant Variable (A)</p>
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Linear regression analysis cannot be used to predict the value of a variable using another variable.

<p>False (B)</p>
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________ gradient descent calculates the gradient of the error function for the entire dataset before updating the weights.

<p>batch</p>
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Is predicting the color of a house a regression task?

<p>No (B)</p>
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Only batch gradient descent uses normalization.

<p>False (B)</p>
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In the equation $y = 2x + 2$, if $x = 5$ what is the result for y?

<p>12</p>
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When finding the MSE (Mean Square Error) is it important to square the error? Is that incorrect? Why or why not?

<p>It is important to square the error. Simply summing up could lead to positive and negative errors canceling out (C)</p>
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Flashcards

Regression

A statistical method used to answer questions regarding amount, like "How much does a house cost?"

Linear Regression Goal

Fitting a line through a dataset of points; identifying the optimum line that best represents the data trend.

Dependent Variable

The variable you want to predict in linear regression.

Independent Variable

The variable used to predict another variable's value in linear regression.

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Mean Squared Error (MSE)

Measures the average squared difference between predicted and actual values; always zero or positive, with lower values indicating better fit.

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Stochastic Gradient Descent

A method that applies the squared (or absolute) trick at every point in the data one by one, repeating the process.

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Batch Gradient Descent

A method that applies the squared (or absolute) trick at every point in the data at the same time, repeating the process.

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Linear Regression

A supervised learning method to predict continuous output variables by fitting a linear equation to observed data.

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Logistic Regression

A Machine Learning algorithm mainly used for classification tasks.

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Logistic Function (Sigmoid Function)

A mathematical function used to map predicted values to probabilities.

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Study Notes

  • Linear regression answers how much questions.
  • Linear regression tries to draw a line through a dataset of points, called fitting.
  • The goal of linear regression is to find the best-fit line that minimizes the difference between predicted and actual observed values.
  • Linear regression assumes the relation between independent and dependent variables are linear.
  • Linear Regression is a supervised learning method.
  • The predicted output will be continuous, meaning it is a regression task.
  • Linear regression analysis predicts a variable's value based on another variable's value, such as predicting house prices based on certain features.
  • The variable to predict is the dependent variable.
  • The variable to predict other variables is the independent variable.

Linear Equation

  • The equation of a line is defined by 𝑦 = 𝑤1 𝑥 + 𝑤2
  • 𝑤1 represents the slope.
  • 𝑤2 represents the y-intercept.

Example House Prediction

  • A small house costs $70,000.
  • A big house costs $160,000.
  • To estimate price, graph house prices, where:
    • The x-axis represents the size of the house in square feet.
    • The y-axis represents the price of the house.

Training

  • Training involves fitting the line using gradient descent (MSE).

Prediction

  • Predictions are made using the equation: 𝑤1 𝑥1 + 𝑤2 𝑥2+⋯+𝑤𝑛 𝑥𝑛 +𝑏
  • Example: For a house of size 500, w1 = 5 and w2 = 100, then the price is calculated as: 5*500+100=2600
  • Example: With a house of size size 500 and 4 bedrooms, where w1 = 5, w2 = 10, and w3 = 100, the price comes to 5500 + 410 + 100.

Mean Squared Error

  • The Mean Squared Error (MSE) measures the average squared difference between estimated and actual values.
  • MSE is always zero or a positive value.
  • Values closer to zero are better.
  • To compute the error over multiple samples such as houses: Error = sum(Actual - Predicted)^2
  • If you sum the error you will get an incorrect result.
  • If you square the error, and get (20)^2= 400.

Error Calculation

  • Error = (Actual - Predicted)^2
    • Example: House 1: actual 120K, predicted 100K -> error 20K -> (20)^2 = 400
    • Example: House 2: actual 60K, predicted 80K -> error -20K -> (-20)^2 = 400
  • You need to normalize to compare errors of batches with different sizes, for example:
  • For example, if you want the average, and want to see which batch size produces a lower error you do the following:
  • Error = average(Actual - Predicted)^2

Gradient Descent Techniques

  • Stochastic gradient descent applies the squared (or absolute) trick at every point in the data one by one, repeating this process many times.
  • Batch gradient descent applies the squared (or absolute) trick at every point in the data all at the same time, repeating this process many times.

Polynomial Regression

  • Used for non-linear datasets.

Logistic Regression

  • It is a supervised machine learning algorithm mainly used for classification tasks.
  • The goal is to predict the probability that an instance belongs to a given class or not.
  • Logistic regression is a statistical algorithm to analyze the relationship between a set of independent variables and the dependent binary variables.
  • Logistic regression is used for determining if an email is spam or not.

Sigmoid Function

  • It is a mathematical function used to map the predicted values to probabilities.
  • f(x) = 1 / (1 + e^(-x))
  • e:
    • Is the Number of Euler
    • Is the base of the natural logarithms.
    • This constant is approximately 2.718
  • x: Can be the output of a Neural Network

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