Q.The principal of a school wants to do following analysis on the basis of food items procured and sold in the canteen:

Create a small price/sales table (our own sample data, as the question asks), then: a) compare purchase vs sale price by the difference (profit per item) — juice ₹5, biscuits ₹2; b) compare the three items' sales with totals/means shown as a bar chart — biscuits sell the most units (200); c) measure variation in same-quantity juice prices across companies with range (₹7) and standard deviation (≈ ₹2.61):

import statistics
juice = [25, 28, 24, 30, 23]
print(max(juice) - min(juice), round(statistics.pstdev(juice), 2))
``` …

Step 1 — create the dataset (sample data we define ourselves)

import pandas as pd

df = pd.DataFrame({
    'Item':          ['Fruit Juice', 'Biscuits', 'Samosa'],
    'PurchasePrice': [20, 10, 8],     # rupees per unit
    'SalePrice':     [25, 12, 10],
    'UnitsSold':     [120, 200, 150]  # units sold this month
})

df['Profit']    = df['SalePrice'] - df['PurchasePrice']
df['SaleValue'] = df['SalePrice'] * df['UnitsSold']
print(df)

Expected output:

Key line: df['Profit'] = df['SalePrice'] - df['PurchasePrice'] — pandas subtracts the columns element-wise, computing every item's margin in one statement.

a) Compare purchase and sale price of fruit juice and biscuits

Technique: the difference between the two prices (the profit per unit). Fruit juice: 25 − 20 = ₹5; biscuits: 12 − 10 = ₹2. Juice earns more per unit; relative to cost, juice marks up 25% and biscuits 20%. A paired bar chart (purchase bar next to sale bar for each item) shows this at a glance.

b) Compare sales of fruit juice, biscuits and samosa

Technique: compare the totals — units sold (and/or sale value) per item, i.e., a simple item-wise aggregate comparison, drawn as a bar chart (x-axis: item; y-axis: units sold). From the dataset: biscuits sell the most units (200), then samosa (150), then juice (120); by revenue, juice leads (₹3000) because of its higher price. Comparing both columns tells the principal what sells most vs what earns most.

c) Variation in sale price of fruit juices of different companies (same quantity)

Take the sale prices of five companies' 200 ml juice packs and apply the measures of variation — range and standard deviation:

import statistics …