VOCAB
A random sample of 30 households was selected as part of a study on electricity usage, and the number of kilowatt-hours was recorded for each household in the sample for the March quarter of 2006. The average usage was found to be 375kWh. In a very large study in the March quarter of the previous year it was found that the standard deviation of the usage was 81kWh. Assuiming the standard deviation is unchanged and that the usage is normally distributed, create a confidence interval for a 99% confidence level for the mean usage in the March quarter of 2006?
I am 99% confident that the true average number of kilowatt-hours for households in March of 2006 is between 336.92kWh and 413.08kWh. Rounded is ok
How many months have 28 days?
Suppose that a market research firm is hired to estimate the percent of adults living in a large city who have cell phones. Five hundred randomly selected adult residents in this city are surveyed to determine whether they have cell phones. Of the 500 people sampled, 421 responded yes - they own cell phones. Using a 95% confidence level, compute a confidence interval estimate for the true proportion of adult residents of this city who have cell phones.
We estimate with 95% confidence that between 81% and 87.4% of all adult residents of this city have cell phones.
Ming works as a quality assurance analyst at a bottling factory. She wants to use a one-sample z interval to estimate what proportion of 500mL bottles are underfilled. She wants the margin of error to be no more than ±4% at 90% confidence. What sample size of bottles should she use?
At least 421
An industrial designer wants to determine the average amount of time it takes an adult to assemble an "easy to assemble" toy. A sample of 16 times yielded an average time of 19.92 minutes, with a sample standard deviation of 5.73 minutes. Normally distributed, provide a 95% confidence interval for the mean assembly time.
I am 95% confident that the true average amount of time it takes an adult to assemble an "easy to assemble" toy is between 17.11 minutes and 22.73 minutes. Rounded is ok!
Which is the world's largest country based on landmass?
Russia
A Pew Research Center report on gamers and gaming estimated that 49% of U.S. adults play video games on a computer, TV, game console, or portable device such as a cell phone. This estimate was based on a random sample of 2001 U.S. adults. Construct a 95% confidence interval for the proportion of all U.S. adults who play video games.
We are 95% confident that the interval from 0.468 to 0.512 captures p = the true proportion of U.S. adults who play video games. Rounding is ok!
What is the z* for an 84% confidence interval
1.405
C is the success rate (capture rate) of the method that produces the interval.
What is a confidence level
The recommended retail price of a brand of designer jeans is $150. The price of the jeans in a sample of 16 retailers is on average $141, with a sample standard deviation of $4. The prices can be assumed to be normally distributed. Construct a 95% confidence interval for the average sale price.
I am 95% confident that the true average retail price of a brand of designer jeans is between $139.04 and $142.96. Rounded is ok!
A group of owls is called ...
Parliament
A 2016 survey of 1480 randomly selected U.S. adults found that 55% of respondents agreed with the following statement: “Organic produce is better for health than conventionally grown produce. Construct a 99% confidence interval for the proportion of all U.S. adults who think that organic produce is better for health than conventionally grown produce
We are 99% confident that the interval from 0.517 to 0.583 captures p = the true proportion of U.S. adults who would agree with the statement “Organic produce is better for health than conventionally grown produce
What is the critical value for a 90% confidence interval with a sample size of 9?
t*=1.86
When asked to construct and interpret a confidence interval, follow the four-step process:
State
Plan
Do
Conclude
Why do we check each of the 3 conditions?
Random --> generalize to the population
10% --> indendence
Large Counts / Large Sample --> sampling dist of p hat/ x bar are approx Normal
Facebook, Twitter, Skype and Instagram are all banned in ...
China, North Korea, and Iran
The shape of the sampling distribution of p(hat) when the sample is large (i.e., np ≥ 10 and n(1 – p)≥ 10) and random is a
What is approximately normal (distribution)
What has 4 wheels and flies?
A garbage truck
What is the number of free choices left after a sample statistic is calculated?
Degrees of freedom
What is the closest planet to the Sun?
Mercury
Tonya wants to estimate what proportion of her school’s seniors plan to attend the prom. She interviews an SRS of 50 of the 750 seniors in her school and finds that 36 plan to go to the prom. Construct a 90% confidence interval for p.
We are 90% confident that the interval from 0.616 to 0.824 captures p = the true proportion of all seniors at Tonya’s high school who plan to attend the prom.
David's parents have three sons: Snap, Crackle, and what's the third son's name?
David