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It seems you've uploaded images that include MATLAB code and a table of test scores for Problem 4.2. Let's break down the problem and guide you through it:

### Problem 4.2 Breakdown:
#### Task a) 
- **Extract the scores and student number for student 5** into a row vector named `student_5`.
   - You'll need to find student 5's row (from the table provided in the image) and create a row vector.

#### Task b)
- **Extract the scores for Test 1 into a column vector** named `test_1`.
   - Take the scores from the first test (all rows, column 2) and store them in a column vector.

#### Task c)
- **Find the standard deviation and variance for each test**.
   - You'll calculate the standard deviation and variance for the three tests and store them in vectors named `test_std` and `test_var`.

#### Task d)
- **Calculate each student's total score and final percentage**.
   - Assuming each test is worth 100 points, sum the scores for each student to get their total, then calculate the percentage for each student.

#### Task e)
- **Create a new array** with total scores and percentages.
   - This array should include the original data plus the total score and final percentage, making a 6-column array named `final_thermo_scores`.

#### Task f)
- **Sort the array based on the final percentage**, in descending order.
   - Sort the `final_thermo_scores` array by the final percentage and name the result `final_sorted`.

---

### Step-by-Step Implementation in MATLAB:

1. **Load the data**: 
   ```matlab
   load thermo_scores.dat
   ```

2. **Task a - Extract Student 5**:
   ```matlab
   student_5 = thermo_scores(5, :);
   ```

3. **Task b - Extract Test 1 scores**:
   ```matlab
   test_1 = thermo_scores(:, 2);  % Assuming Test 1 scores are in column 2
   ```

4. **Task c - Calculate standard deviation and variance**:
   ```matlab
   test_std = std(thermo_scores(:, 2:4));  % Standard deviation for Test 1, 2, 3
   test_var = var(thermo_scores(:, 2:4));  % Variance for Test 1, 2, 3
   ```

5. **Task d - Calculate total score and final percentage**:
   ```matlab
   total_score = sum(thermo_scores(:, 2:4), 2);  % Sum of scores for each student
   final_percent = (total_score / 300) * 100;    % Calculate percentage (out of 300 points)
   ```

6. **Task e - Create the final array**:
   ```matlab
   final_thermo_scores = [thermo_scores total_score final_percent];
   ```

7. **Task f - Sort the array by final percentage**:
   ```matlab
   final_sorted = sortrows(final_thermo_scores, -6);  % Sort by the 6th column (final percentage), descending
   ```

---

### Would you like more details or have any questions about specific steps?

### Follow-up questions:
1. How do you handle loading `.dat` files in MATLAB if the file isn't in the working directory?
2. What does the function `sortrows` do in MATLAB, and why is the second argument negative?
3. How is standard deviation different from variance, and why calculate both?
4. If the tests were weighted differently, how would you modify the percentage calculation?
5. How can you verify that the final sorted data is correct in MATLAB?

### Tip:
When working with matrices in MATLAB, always make sure the dimensions align when performing operations like addition or multiplication.

MATLAB Problem 4.2: Load thermo_scores.dat and process student test scores to compute statistics and rankings.

This problem involves using MATLAB to process a dataset of student test scores, extracting data for specific students, calculating standard deviation and variance, computing total scores and percentages, and sorting the data by final scores. Learn step-by-step how to perform these tasks in MATLAB.

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