Clarissa Barr

Rollins College

Biography

Professional math tutor and credentialed secondary science teacher

Education

BA Biology
Rollins College
MA Teaching Credential
California State University - Northridge

Educator Statistics

Numerade tutor for 4 years
2070 Students Helped

Topics Covered

The Power of Algebraic Language: Unlocking Mathematical Potential
Mastering Equations and Inequalities: Your Guide to Mathematical Success
Understanding Complex Numbers: A Comprehensive Guide
Maximizing Accuracy with Effective Sampling and Data Analysis
Unlocking Insights with Descriptive Statistics: A Comprehensive Guide
Exploring Probability Topics: From Basics to Advanced Strategies
The Normal Distribution
Hypothesis Testing: Understanding the Basics for Accurate Results
Understanding Confidence Intervals and Sample Size

Clarissa's Textbook Answer Videos

0:00
Introductory Statistics

Suppose that you randomly draw two cards, one at a time, without replacement.
G1 = first card is green
G2 = second card is green
a. Draw a tree diagram of the situation.
b. Find P(G1 AND G2).
c. Find P(at least one green).
d. Find P(G2|G1).
e. Are G2 and G1 independent events? Explain why or why not

Chapter 3: Probability Topics
Section 5: Tree and Venn Diagrams
Clarissa Barr
0:00
Elementary Statistics

When Mendel conducted his famous hybridization experiments, he used peas with green pods and yellow pods. One experiment involved crossing peas in such a way that $25 \%$ (or 145 ) of the 580 offspring peas were expected to have yellow pods. Instead of getting 145 peas with yellow pods, he obtained $152 .$ Assume that Mendel's $25 \%$ rate is correct.
a. Find the probability that among the 580 offspring peas, exactly 152 have yellow pods.
b. Find the probability that among the 580 offspring peas, at least 152 have yellow pods.
c. Which result is useful for determining whether Mendel's chimed rate of $25 \%$ is incorrect? (Part (a) or part (b)?)
d. Is there strong evidence to suggest that Mendel's rate of $25 \%$ is incorrect?

Chapter 6: Normal Probability Distributions
Section 6: Normal as Approximation to Binomial
Clarissa Barr
0:00
Elementary Statistics

Using Raw Data.Test the given claim. Identify the null hypothesis, alternative Hypothesis, test statistic, $P$ -value or critical value(s), conclusion about the null Hypothesis, and final conclusion that addresses the original claim. Use the $P$ -value method unless your instructor specifies otherwise.
California Speeding Listed below are recorded speeds (in $\mathrm{mi} / \mathrm{h}$ ) of randomly selected cars traveling on a section of Highway 405 in Los Angeles (based on data from Sigalert). That part of the highway has a posted speed limit of $65 \mathrm{mi} / \mathrm{h}$. Assume that the standard deviation
of speeds is $5.7 \mathrm{mi} / \mathrm{h}$ and use a 0.01 significance level to test the claim that the sample is from
a population with a mcan that is greater than $65 \mathrm{mi} / \mathrm{h}$.

Chapter 8: Hypothesis Testing
Section 4: Testing a Claim About a Mean: $\sigma$ Known
Clarissa Barr
0:00
Elementary Statistics

Use the data set from Appendix $B$ to test the given claim. Identify the null Hypothesis, alternative hypothesis, test statistic, P-value or critical value(s), conclusion about the null hypothesis, and final conclusion that addresses the original claim. Use the P-value method unless your instructor specifies otherwise.
Do the Screws Have a Length of $3 / 4$ in. $?$ A simple random sample of 50 stainless steel sheet metal screws is obtained from those suppled by Crown Bolt, Inc., and the length of each screw is measured using a vernier caliper. The lengths are listed in Dace Set 19 of Appendix B. Assume that the standard deviation of all such lengths is 0.012 in. and use a 0.05 significance level to test the claim that the screws have a mean length equal to $3 / 4$ in. (or 0.75 in.), as indicated on the package labels. Do the screw lengths appear to be consistent with the package label?

Chapter 8: Hypothesis Testing
Section 4: Testing a Claim About a Mean: $\sigma$ Known
Clarissa Barr
0:00
The Practice of Statistics for AP

One of the most important nongovernment surveys in the United States is the National Opinion Research Center's General Social Survey. The GSS regularly monitors public opinion on a wide variety of political and social issues. Interviews are conducted in person in the subject's home. Are a subject's responses to GSS questions anonymous, confidential, or both? Explain your answer.

Chapter 4: Designing Studies
Section 3: Using Studies Wisely
Clarissa Barr
1 2

Clarissa's Quick Ask Videos

03:21
Intro Stats / AP Statistics

In a certain game of chance, a wheel consists of slots numbered 00, 0, 1, 2,..., . To play the game, a metal ball is spun around the wheel and is allowed to fall into one of the numbered slots. Complete parts (a) through (c) below.

(a) Determine the sample space. Choose the correct answer below.
A. The sample space is {1, 2,..., 32}.
B. The sample space is {00, 0}.
C. The sample space is {00}.
D. The sample space is {00, 0, 1, 2,..., 32}.

(b) Determine the probability that the metal ball falls into the slot marked 3. Interpret this probability.
The probability that the metal ball falls into the slot marked 3 is [probability]. Interpret this probability. Select the correct choice below and fill in the answer box within your choice. (Type a whole number.)
A. If the wheel is spun 1000 times, it is expected that about [probability] of those times result in the ball landing in slot 3.
B. If the wheel is spun 1000 times, it is expected that exactly [probability] of those times result in the ball not landing in slot 3.

(c) Determine the probability that the metal ball lands in an odd slot. Interpret this probability.
The probability that the metal ball lands in an odd slot is [probability]. Interpret this probability. Select the correct choice below and fill in the answer box within your choice. (Type a whole number.)
A. If the wheel is spun 100 times, it is expected that exactly [probability] of those times result in the ball not landing on an odd number.
B. If the wheel is spun 100 times, it is expected that about [probability] of those times result in the ball landing on an odd number.

Clarissa Barr
04:05
Intro Stats / AP Statistics

Mrs Reena has regularly contacted three companies (A, B, and C) for her quarterly servicing of aircons. If A services her aircons, the probability that there will be no problem with the aircons in the next quarter is 0.8. The same probability for B is 0.7 and for C is 0.6. If all her aircons do not show any problems, she will engage the same company in the next quarter. If any of the aircons show a problem, then she will engage A with a probability of 0.5, B with a probability of 0.3, or C with a probability of 0.2 in the next quarter. One of her aircons had a problem last quarter. (i) Identify the probability that her aircons will have no problem in the next quarter. (ii) Given that her aircons had no problem in the next quarter, what is the probability that she engaged C? (iii) What is the probability that she will engage A for the next two quarters?

A study showed that the length of human pregnancies is normally distributed with a mean of 266 days and a standard deviation of 16 days. (i) If a pregnant woman is randomly selected, identify the probability that her length of pregnancy is between 260 and 270 days. (ii) If twenty (20) women are randomly selected, report the probability that the mean length of pregnancies is greater than 265 days.

Clarissa Barr
04:11
Intro Stats / AP Statistics

a. In a door-to-door survey, residents of a neighborhood are asked how many times over the past year they (or anyone in their household) have been the victims of any type of crime.
b. Parole board members rate inmate behavior on a scale with values ranging from 1 to 10; a score of 1 represents exemplary behavior.
c. One hundred college students are asked whether they have ever been arrested.
d. A researcher checks prison records to determine the racial background of prisoners assigned to a particular cell block.
e. A criminologist measures the diameters (in centimeters) of the skulls of inmates who have died in prison, in an attempt to develop a biological theory of the causes of criminality.

Clarissa Barr
00:49
Intro Stats / AP Statistics

A horticulturist working for a large plant nursery is conducting
experiments on the growth rate of a new shrub. Based on previous
research, the horticulturist feels the average weekly growth rate
of the new shrub is 2cm per week. A random sample
of 40 shrubs has an average growth of 1cm per
week with a standard deviation of 2cm. Is there
overwhelming evidence to support the claim that the growth rate of
the new shrub is less than 2cm per week at
a 0.025 significance level?
Step 1 of 3 :
Find the value of the test statistic. Round your answer to three
decimal places, if necessary.

Clarissa Barr
01:42
Intro Stats / AP Statistics

A recent report indicated that 47% of teenagers aged 12-14 own
smartphones. For a random sample of 200 teenagers aged 12-14, what
is the probability that between 35% and 40% of them own a
smartphone? Accurately round your answer to FOUR decimal places. Do
NOT round whatsoever prior to your final answer.

Clarissa Barr
01:15
Intro Stats / AP Statistics

A city councilor asks your advice on how many householders
should be polled in order to gauge the support for a tax increase
to build more schools.1. The councilor wants
to assess the support with a margin of error no more than 0.049
with 95% confidence. What sample size would you recommend if the
councilor has no information about the proportion of householders
who would support a tax increase?Round your ?āˆ—zāˆ— value to
three decimal places when calculating your
answer. Give your answer as an integer.
?=
2. Suppose you conduct the survey and
construct a 99% confidence interval for the true proportion of
householders who are in favor of the tax increase to be (0.47,
0.562). Determine whether the statements below are correct or
incorrect interpretations of the confidence interval.
A. Correct
B. Incorrect
? Correct Incorrect
1. There is a 99% chance that
51.6% of householders are in favor of the tax increase.
? Correct Incorrect
2. We can expect that 99% of the
intervals we construct using this method will contain the true
proportion of householders who are in favor of the tax
increase.
? Correct Incorrect
3. We can be 99% confident that
the true proportion of householders who are in favor of the tax
increase is contained in the interval (0.47, 0.562).
? Correct Incorrect
4. If we collected another random
sample of the same size, there is a 99% chance the new sample
proportion will be between 0.47 and 0.562.
? Correct Incorrect
5. 99% of the time, the true
proportion of householders that are in favor of the tax increase is
between 0.47 and 0.562.

Clarissa Barr
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