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91Ó°ÊÓ

Determine the expected counts for each outcome. $$ \begin{array}{lllll} \hline \boldsymbol{n}=\mathbf{7 0 0} & & & & \\ \hline p_{i} & 0.15 & 0.3 & 0.35 & 0.20 \\ \hline{\text {Expected counts }} & & & & \\ \hline \end{array} $$

Short Answer

Expert verified
105, 210, 245, and 140.

Step by step solution

01

- Identify total number of trials

The total number of trials is denoted by \(n\). Here, \(n = 700\).
02

- Identify probabilities for each outcome

The probabilities for each outcome are given as \(p_1 = 0.15, p_2 = 0.3, p_3 = 0.35, p_4 = 0.20\).
03

- Calculate the expected count for each outcome

The formula to calculate the expected count for each outcome is \(E_i = n \times p_i\).
04

- Compute expected count for first outcome

Using the formula: \(E_1 = 700 \times 0.15 = 105\).
05

- Compute expected count for second outcome

Using the formula: \(E_2 = 700 \times 0.3 = 210\).
06

- Compute expected count for third outcome

Using the formula: \(E_3 = 700 \times 0.35 = 245\).
07

- Compute expected count for fourth outcome

Using the formula: \(E_4 = 700 \times 0.20 = 140\).
08

- Compile all expected counts

The expected counts for each outcome are 105, 210, 245, and 140.

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Key Concepts

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

Overview of Probabilities
Understanding probabilities is essential for determining expected counts. Probabilities represent the likelihood that a particular event will occur. In this exercise, the probabilities for four different outcomes were given:
  • \( p_1 = 0.15 \)
  • \( p_2 = 0.3 \)
  • \( p_3 = 0.35 \)
  • \( p_4 = 0.20 \)
All these probabilities add up to 1, which means one of these four outcomes will surely happen in each trial. Probabilities are always between 0 and 1, inclusive.
Number of Trials Explained
The total number of trials, denoted by \(n\), signifies how many times an experiment or event is conducted. In the given exercise, the number of trials is provided as \( n = 700 \). Each trial is an independent instance where one of the four outcomes will occur. The greater the number of trials, the more accurate our expected counts will be, following the Law of Large Numbers. In simple terms, more trials give us a better representation of the probabilities given.
Determining Expected Outcomes
Expected outcomes refer to the predicted frequency of each outcome based on the probabilities and the number of trials. The formula used to compute the expected count for each outcome is:
\[ E_i = n \times p_i \]
Here, \(E_i\) stands for the expected count of the \(i\)-th outcome, \(n\) is the total number of trials, and \(p_i\) is the probability of the \(i\)-th outcome. By substituting the given values in the formula, we found:
  • For the first outcome: \( E_1 = 700 \times 0.15 = 105 \)
  • For the second outcome: \( E_2 = 700 \times 0.3 = 210 \)
  • For the third outcome: \( E_3 = 700 \times 0.35 = 245 \)
  • For the fourth outcome: \( E_4 = 700 \times 0.20 = 140 \)
These calculations show how frequently we can expect each outcome to occur out of 700 trials.
Applying Statistical Formulas
Statistical formulas are crucial for analyzing and interpreting data in experiments. In the context of this exercise, we used the expected count formula:

\[ E_i = n \times p_i \]
This simple yet powerful formula helps to predict the outcome frequencies. Another key aspect is understanding the sum of probabilities. They should total to 1 to ensure all possible outcomes are accounted for. Using these fundamental concepts allows us to effectively interpret and build upon data, leading to accurate insights and informed conclusions. Remember, ensuring accuracy in applying these formulas is key to sound statistical analysis.

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Most popular questions from this chapter

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At Joliet Junior College, the mathematics department decided to offer a redesigned course in Intermediate Algebra, called the Math Redesign Program (MRP). Laura Egner, the coordinator of the program, wanted to determine if the grade distribution in the course differed from that of traditional courses. The following shows the grade distribution of traditional courses based on historical records and the observed grades in three pilot classes in which the MRP program was utilized. $$ \begin{array}{lcccccc} & \mathbf{A} & \mathbf{B} & \mathbf{C} & \mathbf{D} & \mathbf{F} & \mathbf{W} \\\ \hline \begin{array}{l} \text { Traditional } \\ \text { Distribution } \end{array} & 0.133 & 0.191 & 0.246 & 0.104 & 0.114 & 0.212 \\ \hline \begin{array}{l} \text { Observed Counts } \\ \text { in MRP Program } \end{array} & 7 & 16 & 10 & 13 & 6 & 12 \\ \hline \end{array} $$ (a) How many students were enrolled in the MRP program for the three pilot courses? Based on this result, determine the expected number of students for each grade assuming there is no difference in the distribution of MRP student grades and traditional grades. (b) Does the sample evidence suggest that the distribution of grades is different from the traditional classes at the \(\alpha=0.01\) level of significance? (c) Explain why it makes sense to use 0.01 as the level of significance. (d) Suppose the MRP pilot program continues in three more classes with the grades earned for all six pilot courses shown below. Notice that the sample size was simply doubled with the grade distribution remaining unchanged. Does this sample evidence suggest that the distribution of grades is different from the traditional classes at the \(\alpha=0.01\) level of significance? What does this result suggest about the role of sample size in the ability to reject a statement in the null hypothesis? $$ \begin{array}{lcccccc} & \mathbf{A} & \mathbf{B} & \mathbf{C} & \mathbf{D} & \mathbf{F} & \mathbf{W} \\\ \hline \begin{array}{l} \text { Observed Counts } \\ \text { in MRP Program } \end{array} & 14 & 32 & 20 & 26 & 12 & 24 \end{array} $$

In Section 10.2, we tested hypotheses regarding a population proportion using a z-test. However, we can also use the chi-square goodness-of-fit test to test hypotheses with \(k=2\) possible outcomes. In Problems 25 and \(26,\) we test hypotheses with the use of both methods. According to the U.S. Census Bureau, \(7.1 \%\) of all babies born are of low birth weight \((<5 \mathrm{lb}, 8 \mathrm{oz})\) An obstetrician wanted to know whether mothers between the ages of 35 and 39 years give birth to a higher percentage of low-birth-weight babies. She randomly selected 240 births for which the mother was 35 to 39 years old and found 22 low-birth-weight babies. (a) If the proportion of low-birth-weight babies for mothers in this age group is \(0.071,\) compute the expected number of low-birth-weight births to 35 - to 39 -year-old mothers. What is the expected number of births to mothers 35 to 39 years old that are not low birth weight? (b) Answer the obstetrician's question at the \(\alpha=0.05\) level of significance using the chi-square goodness-of-fit test. (c) Answer the question by using the approach presented in Section 10.2

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