Answer:
Standard error
Step-by-step explanation:
The standard deviation of the distribution of sample means is called the standard error of the means.
It is denoted by: 
The standard error is calculated using the formula: 
where n is the sample size and 
is the population standard deviation.
They are both equal to 2/10 because 4/10 divided by 2 is the same as 4/10 x 1/2
Subtract 6 from both sides (8n=40) then divide 40 by 8 (5) so n=5
Answer:
10 km/hr
Step-by-step explanation:
The aircraft carrier and the container ship both took 30 hours to travel their respective distances. If you divide both numbers by 30, you find that their differences is 5. We can tell that the aircraft carrier traveled 450 ÷ 30 = 15 km/hr and the container ship traveled at a speed of 300 ÷ 30 = 10 km/hr. The aircraft carrier traveled 5 km/hr faster. So, we can tell the container ship traveled at 10 km/hr.
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