Why statistical tools drive decisions in MATLAB - See It in Action

Why Statistical Tools Drive Decisions

📖 Scenario: Imagine you run a small store and want to understand which products sell best. You have sales data for different products over a week. Using simple statistics, you can make better decisions about what to stock more or less.

🎯 Goal: You will create a MATLAB program that stores sales data, sets a sales threshold, finds products that sell above this threshold using statistical comparison, and then displays these products. This shows how statistics help in making smart business choices.

📋 What You'll Learn

Create a dictionary (containers.Map) with product names as keys and their sales numbers as values

Create a variable to hold the sales threshold

Use a loop to find products with sales above the threshold

Display the list of products that meet the sales criteria

💡 Why This Matters

🌍 Real World

Small business owners use sales data and simple statistics to decide which products to stock more or less, improving profits and reducing waste.

💼 Career

Data analysts and business managers use statistical tools to interpret data and make informed decisions that guide company strategies.

1

DATA SETUP: Create sales data dictionary

Create a containers.Map called salesData with these exact entries: 'Apples' with value 150, 'Bananas' with value 90, 'Cherries' with value 120, 'Dates' with value 60, and 'Elderberries' with value 30.

MATLAB

% Your code here to create salesData map

Hint

Use containers.Map with two cell arrays: one for keys (product names) and one for values (sales numbers).

2

CONFIGURATION: Set sales threshold

Create a variable called threshold and set it to 100.

MATLAB

salesData = containers.Map({'Apples', 'Bananas', 'Cherries', 'Dates', 'Elderberries'}, [150, 90, 120, 60, 30]);
% Your code here to set threshold

Hint

Just create a simple variable threshold and assign the number 100.

3

CORE LOGIC: Find products with sales above threshold

Create a cell array called topProducts. Use a for loop with variable product to iterate over salesData.keys(). Inside the loop, get the sales value for product from salesData. If the sales value is greater than threshold, add product to topProducts.

MATLAB

salesData = containers.Map({'Apples', 'Bananas', 'Cherries', 'Dates', 'Elderberries'}, [150, 90, 120, 60, 30]);
threshold = 100;
% Your code here to find topProducts

Hint

Initialize topProducts as an empty cell array. Loop over keys using salesData.keys(). Use salesData(product) to get sales. Use if to check sales > threshold and add product to topProducts.

4

OUTPUT: Display products with sales above threshold

Use disp to display the text 'Products with sales above 100:'. Then use disp to display the topProducts cell array.

MATLAB

salesData = containers.Map({'Apples', 'Bananas', 'Cherries', 'Dates', 'Elderberries'}, [150, 90, 120, 60, 30]);
threshold = 100;
topProducts = {};
keysList = salesData.keys();
for i = 1:length(keysList)
    product = keysList{i};
    sales = salesData(product);
    if sales > threshold
        topProducts{end+1} = product;
    end
end
% Your code here to display results

Hint

Use disp twice: once for the message, once for the list topProducts.

Practice

1. Why do we use statistical tools like mean and std in MATLAB when making decisions?

easy

A. To make the code run faster

B. To change the data values randomly

C. To understand data patterns and make informed decisions

D. To create graphics only

Solution

1. Step 1: Understand the purpose of statistical tools

   Statistical tools like mean and standard deviation help summarize data and show patterns.

2. Step 2: Connect tools to decision making

   By understanding data patterns, we can make better, informed decisions rather than guessing.

3. Final Answer:

   To understand data patterns and make informed decisions -> Option C

4. Quick Check:

   Statistical tools guide decisions = B [OK]

Hint: Statistical tools summarize data to guide decisions [OK]

Common Mistakes:

• Thinking statistical tools speed up code
• Believing they randomly change data
• Assuming they only create graphics

2. Which MATLAB command correctly calculates the average of the vector A = [4, 8, 12]?

easy

A. average(A)

B. mean(A)

C. sum(A)

D. std(A)

Solution

1. Step 1: Identify the function for average in MATLAB

   The function mean() calculates the average of numbers in a vector.

2. Step 2: Check other options

   average() is not a MATLAB function, sum() adds values, and std() calculates standard deviation.

3. Final Answer:

   mean(A) -> Option B

4. Quick Check:

   Average = mean() [OK]

Hint: Use mean() to find average in MATLAB [OK]

Common Mistakes:

• Using average() which is not a MATLAB function
• Confusing sum() with average
• Using std() instead of mean()

3. What is the output of this MATLAB code?

A = [2, 4, 6, 8];
m = mean(A);
s = std(A);
disp([m, s]);

medium

A. [5 2.58199]

B. [4 2]

C. [6 3]

D. [5 3]

Solution

1. Step 1: Calculate the mean of A

   Mean = (2 + 4 + 6 + 8) / 4 = 20 / 4 = 5.

2. Step 2: Calculate the standard deviation of A

   Standard deviation ≈ 2.58199 for these values.

3. Final Answer:

   [5 2.58199] -> Option A

4. Quick Check:

   mean = 5, std ≈ 2.58 [OK]

Hint: Calculate mean and std separately, then display [OK]

Common Mistakes:

• Mixing up mean and std values
• Calculating sum instead of mean
• Using wrong formula for std

4. Find the error in this MATLAB code that tries to calculate the mean of B = [1, 3, 5, 7]:

B = [1, 3, 5, 7];
average = mean(B);
disp(average);

medium

A. mean() function is not defined in MATLAB

B. Missing semicolon after mean(B)

C. disp() cannot display variables

D. Variable name 'average' overwrites a function

Solution

1. Step 1: Check variable naming

   Using 'average' as a variable name is allowed but can confuse readers since it looks like a function name.

2. Step 2: Confirm syntax correctness

   There is no syntax error; semicolon is optional for suppressing output, mean() is a valid function, and disp() can display variables.

3. Final Answer:

   Variable name 'average' overwrites a function -> Option D

4. Quick Check:

   Variable name shadows function = C [OK]

Hint: Avoid naming variables same as functions [OK]

Common Mistakes:

• Thinking semicolon is mandatory
• Believing mean() is undefined
• Assuming disp() can't show variables

5. You have two data sets in MATLAB:

data1 = [10, 20, 30, 40];
data2 = [15, 25, 35, 45];

Which statistical tool helps decide if the difference between these sets is significant for decision making?

hard

A. t-test

B. std

C. sum

D. mean

Solution

1. Step 1: Understand the goal

   We want to check if the difference between two data sets is statistically significant.

2. Step 2: Identify the correct statistical test

   Mean and std show averages and spread but do not test significance. The t-test compares means to check significance.

3. Final Answer:

   t-test -> Option A

4. Quick Check:

   Significance test = t-test [OK]

Hint: Use t-test to compare two data sets statistically [OK]

Common Mistakes:

• Using mean or std to test significance
• Confusing sum with statistical tests
• Ignoring the need for a significance test