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Independent? In 2015 , the Report on the LC Berkeley Faculty Salary Equity Study shows that 87 of the university's 222 assistant professors were women, along with 137 of the 324 associate professors and 243 of the 972 full professors. (a) What is the probability that a randomly chosen Berkeley professor (of any rank) is a woman? (b) What is the conditional probability that a randomly chosen professor is a woman, given that the person chosen is a full professor? (c) Are the rank and sex of Berkeley professors independent? How do you know?

Short Answer

Expert verified
a) 0.3076; b) 0.2500; c) Not independent, probabilities differ.

Step by step solution

01

Calculate Total Number of Professors

Before calculating the probabilities, we need to find the total number of professors. Add up the assistant, associate, and full professors. Total number of professors = 222 (assistant) + 324 (associate) + 972 (full) = 1518.
02

Calculate Total Number of Women Professors

Add the number of women in each category to find the total number of women professors: Total women professors = 87 (assistant) + 137 (associate) + 243 (full) = 467.
03

Calculate Probability of a Woman Professor (Part a)

The probability that a randomly chosen professor is a woman is the number of women professors divided by the total number of professors.Probability = \( \frac{467}{1518} \approx 0.3076 \).
04

Conditional Probability of a Woman Given Full Professor (Part b)

For part (b), we are looking at the conditional probability that a professor is a woman given that they are a full professor. First, calculate the total number of full professors, which is given as 972. Then use the number of woman full professors, which is 243.Conditional probability = \( \frac{243}{972} \approx 0.2500 \).
05

Determine Independence of Rank and Gender (Part c)

In probability, two events are independent if the probability of one event is the same regardless of whether the other event occurs. Rank and gender are independent if the probability of being a woman is the same across all ranks.Compare the overall probability of any professor being a woman (Step 3, \(0.3076\)) with the conditional probability for full professors (Step 4, \(0.2500\)). Since the probabilities are different, rank and gender are not independent.

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Key Concepts

These are the key concepts you need to understand to accurately answer the question.

Conditional Probability
Conditional probability involves calculating the likelihood of an event, given that another event has already occurred. It helps us refine our calculations by considering specific circumstances.
For instance, in our example, we calculate the probability of a professor being a woman, provided we already know they are a full professor. Here's how we approached it:
1. Identify the subset of full professors.
2. Find how many of these full professors are women.
3. Divide the number of woman full professors by the total number of full professors (from Step 4).So, the conditional probability of the professor being a woman, given they are full professors, is calculated as:\[P( ext{Woman} \,|\, ext{Full Professor}) = \frac{243}{972} \approx 0.2500\]This tells us there's a 25% chance a randomly chosen full professor is a woman.
Independence Test
The concept of independence in probability means that two events are unrelated. The occurrence of one does not influence or change the probability of the other.
In terms of gender and rank among Berkeley professors, we check if these factors are independent. To do this, we compare two probabilities:
- The probability of being a woman regardless of rank.
- The conditional probability of being a woman given a specific rank (like full professor). For the situation to display independence, both probabilities need to match. However, we found that the overall chance of a professor being a woman is approximately 30.76% (from Step 3), whereas for full professors specifically, the chance is around 25% (from Step 4).
These differing probabilities reveal that rank and gender at Berkeley are not independent.
Probability Calculation
Probability calculations help quantify the likelihood of particular outcomes. They are a fundamental part of assessing scenarios in statistics.
In the given exercise, we started by determining the overall probability of a professor being a woman. Here's the process:1. Count the total number of professors across all ranks.
2. Add up all female professors from each rank.
3. Divide the total number of female professors by the total number of professors.Our final calculation, as shown in Step 3, expressed as:\[P( ext{Woman}) = \frac{467}{1518} \approx 0.3076\]This means there's roughly a 31% chance that a randomly chosen professor is a woman from Berkeley.
Gender Statistics
Gender statistics provide insight into the distribution of genders within a particular group, helping us understand statistical representation.
In the Berkeley professor example, we categorize data by gender within each rank: - **Assistant Professors**: 87 of 222 are women.
- **Associate Professors**: 137 of 324 are women.
- **Full Professors**: 243 of 972 are women. These statistics reveal that only a portion of each rank is represented by women, and collectively, they make up a certain fraction of the entire faculty.
Analyzing such distributions can aid in identifying any gender disparities and discussing potential solutions to address equity in representation.

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