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Relative frequency and expected outcomes

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शिक्षकों के लिए: Relative frequency and expected outcomes (Mathematics, Probability) के लिए इस्तेमाल के लिए तैयार लेसन स्लाइड्स, रिवीज़न नोट्स — इन्हें अपने लेसन में इस्तेमाल करें, या टॉपिक को एक इंटरैक्टिव क्लास एक्टिविटी की तरह चलाएं जिसे आपके शिक्षार्थी लाइव गेम की तरह खेलें।

लेसन नोट्स

Theoretical and experimental probability

  • Theoretical probability = number of favourable outcomes ÷ total equally likely outcomes. A fair die gives P(6) = \frac{1}{6}.
  • Relative frequency (experimental probability) = number of times the event happened ÷ total number of trials.
  • Probabilities lie between 0 (impossible) and 1 (certain), and all outcomes sum to 1: P(A) + P(\text{not } A) = 1.

Relative frequency and the law of large numbers

  • Over many independent trials with a stable underlying probability, relative frequency tends to settle near that probability. More trials generally reduce random variation, but do not guarantee a closer estimate at every step or remove systematic bias.
  • A spinner landing on red 18 times in 50 spins has relative frequency \frac{18}{50} = 0.36.

Expected outcomes

  • Expected number = probability × number of trials. If P(\text{red}) = 0.2 and there are 150 trials, expect 0.2 \times 150 = 30.
  • Expected values are averages; actual results vary.

Expected frequencies

Expected frequenciesProbabilityTrialsExpected count0.2150300.55002500.02250050

Bias and fairness

  • If the relative frequencies are very different from equal values over many trials, the die or coin may be biased.
  • Compare experimental results to the theoretical probability to judge fairness.

Estimating probabilities

  • Use data (e.g. past weather) to estimate probability when outcomes are not equally likely.

स्लाइड्स

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प्रैक्टिस सवाल

फ्री प्रीव्यू — 32 में से 8 सवाल। सभी देखने के लिए साइन अप करें।
  1. 1.What is the probability of an impossible event?

    Easy
    • A0
    • B0.5
    • C1
    • D-1
  2. 2.What is P(\text{even}) when a fair die is rolled?

    Easy
    • A\frac{1}{6}
    • B\frac{1}{3}
    • C\frac{1}{2}
    • D\frac{2}{3}
  3. 3.A coin lands on heads 30 times in 100 tosses. What is the relative frequency of heads?

    Easy
    • A0.3
    • B0.7
    • C30
    • D0.5
  4. 4.If P(\text{rain}) = 0.35, what is P(\text{no rain})?

    Easy
    • A0.65
    • B0.35
    • C0.45
    • D1.35
  5. 5.A spinner has P(\text{red}) = 0.2. How many reds do you expect in 150 spins?

    Easy
    • A15
    • B20
    • C30
    • D75
  6. 6.A bag has 3 red and 7 blue counters. What is P(\text{red})?

    Easy
    • A\frac{3}{7}
    • B\frac{3}{10}
    • C\frac{7}{10}
    • D\frac{1}{3}
  7. 7.In 200 trials an event occurs 50 times. What is the relative frequency?

    Easy
    • A0.25
    • B0.5
    • C4
    • D0.05
  8. 8.For independent trials under unchanged conditions, why does a large sample generally give a more reliable probability estimate than a small sample?

    Easy
    • Arandom fluctuations in the relative frequency are typically smaller
    • Bit is quicker
    • Cit is always exact
    • Dthere is no difference

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