Answer:
The temperature dropped 48 degrees in 12 hours.
Step-by-step explanation:
4×12=48
Answer:
20 x 30 + 11 - 8
Step-by-step explanation:
Answer:
18 3/4 miles
Step-by-step explanation:
convert fractions into decimals and multiply 12.5 by 1.5 to get your answer and then convert back to fractions
Answer:
The number of observations required is closest to 609 ⇒ b
Step-by-step explanation:
The formula of the sample size is n = [( . σ)/E]² , where
- σ is the standard deviation
- E is the margin of error
- is the z-score, where 1 - α = confidence interval
∵ We want 90% confidence interval for the average amount
spent on books by freshmen in their first year at a major
university
∴ 1 - α = 90%
∵ 90% = 90 ÷ 100 = 0.90
∴ 1 - α = 0.90
- Subtract 1 from both sides
∴ - α = -0.10
- Divide both sides by -1
∴ α = 0.10
- Find the value of
∴ = = 0.05
- Look to the normal distribution table to find z-score for this
value with opposite sign
∴ = 1.645
∵ The interval is to have a margin of error of $2
∴ E = 2
∵ We estimate that the standard deviation of the amount spent
will be close to $30
∴ σ = 30
- Substitute these values in the formula above
∴ n = [(1.645)(30) ÷ 2]²
∴ n = 608.855
- Round it to the whole number
∴ n = 609
The number of observations required is closest to 609