National surveys indicate that 36% of people have been in a car accident in the last 5 years. If you randomly sample 10 people, how likely is that exactly 4 have had an accident in the last 5 years?
Table of contents
- 1. Introduction to Statistics53m
- 2. Describing Data with Tables and Graphs2h 1m
- 3. Describing Data Numerically1h 48m
- 4. Probability2h 26m
- 5. Binomial Distribution & Discrete Random Variables2h 55m
- 6. Normal Distribution & Continuous Random Variables1h 48m
- 7. Sampling Distributions & Confidence Intervals: Mean2h 8m
- 8. Sampling Distributions & Confidence Intervals: Proportion1h 20m
- 9. Hypothesis Testing for One Sample2h 23m
- 10. Hypothesis Testing for Two Samples3h 25m
- 11. Correlation1h 6m
- 12. Regression1h 4m
- 13. Chi-Square Tests & Goodness of Fit1h 30m
- 14. ANOVA1h 4m
5. Binomial Distribution & Discrete Random Variables
Binomial Distribution
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A biologist is monitoring a large bird sanctuary where a particular bird species is known to have a 70% success rate for each nesting attempt (at least one chick fledges from the nest). This season, she observes 500 independent nesting attempts across the sanctuary.
(B) What is the probability that less than 330 attempts are successful?
A
0.02
B
0.005
C
0.98
D
0.03

1
Step 1: Recognize that this is a binomial probability problem. The number of successful nesting attempts follows a binomial distribution because there are a fixed number of trials (500), each trial is independent, and there are only two outcomes (success or failure). The probability of success for each trial is 70% (p = 0.7).
Step 2: Approximate the binomial distribution using a normal distribution. Since the number of trials (n = 500) is large, the binomial distribution can be approximated by a normal distribution with mean (μ) and standard deviation (σ). Calculate the mean using the formula: μ = n × p. Calculate the standard deviation using the formula: σ = √(n × p × (1 - p)).
Step 3: Standardize the problem to a z-score. To find the probability that less than 330 attempts are successful, first convert the value 330 to a z-score using the formula: z = (X - μ) / σ, where X is the value of interest (330), μ is the mean, and σ is the standard deviation.
Step 4: Use the z-score to find the cumulative probability. Once the z-score is calculated, use a standard normal distribution table or a statistical software to find the cumulative probability corresponding to the z-score. This cumulative probability represents the probability that the number of successful attempts is less than 330.
Step 5: Interpret the result. The cumulative probability obtained from the z-score is the answer to the question. Compare this probability to the provided answer choices to identify the correct one.
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