Probability Distributions — Flashcards
Tamil Nadu Board · Class 12 · Mathematics
20 flashcards for Probability Distributions (Tamil Nadu Board Class 12 Mathematics) to test yourself on key terms and facts.
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Two coins are tossed simultaneously. Find the probability mass function for the number of heads occurred.
Answer
Step 1: Identify sample space: S = {TT, TH, HT, HH} Step 2: Let X = number of heads - X(TT) = 0 - X(TH) = 1 - X(HT) = 1 - X(HH) = 2 Step 3: Count frequencies - X = 0: 1 outcome (TT) - X = 1: 2 outco…
A pair of fair dice is rolled once. X denotes the total score. Find P(X = 7) and P(X ≥ 10).
Answer
Step 1: Identify total outcomes - Total outcomes when rolling two dice = 36 Step 2: Find outcomes where X = 7 Pairs that sum to 7: (1,6), (2,5), (3,4), (4,3), (5,2), (6,1) Number of favorable outcome…
The probability mass function is: f(x) = 1/30 for x = 1, 2/30 for x = 2, 6/30 for x = 3, 5/30 for x = 4, 6/30 for x = 5, 10/30 for x = 6. Find P(2 < X < 6) and P(X ≤ 4).
Answer
Step 1: Verify that f(x) is a valid PMF Sum = 1/30 + 2/30 + 6/30 + 5/30 + 6/30 + 10/30 = 30/30 = 1 ✓ Step 2: Calculate P(2 < X < 6) This means X can be 3, 4, or 5 (not including 2 and 6) P(2 < X < 6)…
Given CDF: F(x) = 0 for x < -2, F(x) = 0.25 for -2 ≤ x < -1, F(x) = 0.60 for -1 ≤ x < 0, F(x) = 0.90 for 0 ≤ x < 1, F(x) = 1 for x ≥ 1. Find the PMF and calculate P(X < 0) and P(X ≥ -1).
Answer
Step 1: Extract PMF from CDF using f(x) = F(x) - F(x⁻) Jump at x = -2: f(-2) = F(-2) - F(-2⁻) = 0.25 - 0 = 0.25 Jump at x = -1: f(-1) = F(-1) - F(-2) = 0.60 - 0.25 = 0.35 Jump at x = 0: f(0) = F(0) - …
When do you use cumulative distribution function (CDF) instead of probability mass function (PMF)? Provide an example.
Answer
Use CDF when you need: 1. Probability that X is less than or equal to a specific value: P(X ≤ a) 2. Probability within a range: P(a < X ≤ b) = F(b) - F(a) 3. Probability that X exceeds a value: P(X > …
Find the constant C such that f(x) = Cx² for 1 < x < 4 (and 0 otherwise) is a probability density function. Then calculate P(1.5 < X < 3).
Answer
Step 1: Use the condition ∫_{-∞}^{∞} f(x)dx = 1 ∫_{-∞}^{∞} f(x)dx = ∫_1^4 Cx² dx = 1 Step 2: Evaluate the integral C[x³/3]_1^4 = 1 C[(4³/3) - (1³/3)] = 1 C[(64/3) - (1/3)] = 1 C[63/3] = 1 21C = 1 C …
A continuous random variable X has CDF: F(x) = 0 for x < 0, F(x) = x for 0 ≤ x < 1, F(x) = 1 for x ≥ 1. Find the PDF f(x) and calculate P(0.2 ≤ X ≤ 0.7).
Answer
Step 1: Find PDF by differentiating CDF f(x) = dF(x)/dx For x < 0: f(x) = d(0)/dx = 0 For 0 ≤ x < 1: f(x) = d(x)/dx = 1 For x ≥ 1: f(x) = d(1)/dx = 0 Therefore: f(x) = 1 for 0 < x < 1 f(x) = 0 other…
Two balls are selected from an urn with 6 white and 4 black balls. You win ₹20 for each black ball and lose ₹10 for each white ball. Find E(X) where X is winning amount.
Answer
Step 1: Identify possible outcomes and X values - 2 black balls: X = 2(20) = ₹40 - 1 black, 1 white: X = 20 - 10 = ₹10 - 2 white balls: X = -2(10) = -₹20 Step 2: Calculate total ways and favorable ou…
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