A grocery store wants to know how many times a month their customers shop in their store. A card is mailed to the homes of customers who live in the area asking them to participate in an online survey. The results of the survey are complied from the customers who did the online survey.
What type of sampling is this?
• systematic
self-selection
convenience
random
Betty's Bite-Size Candies are packaged in bags. The number of candies per bag is normally distributed, with a mean of 50 candies and a standard deviation of 3. At a quality control checkpoint, a sample of bags is checked, and 4 bags contain fewer than 47 candies. How many bags were probably taken as samples?
5 bags
8 bags
12 bags
25 bags
City officials are trying to estimate how many vehicles travel through a given intersection each day. Which data collection method will most likely provide a biased estimate of the daily number of vehicles that travel through the intersection?
Count the number of vehicles traveling through the intersection every Saturday and Sunday for a month and find the average number per day.
Count the number of vehicles traveling through the intersection each day for a week, and find the median number of vehicles per day.
Count the number of vehicles traveling through the intersection on each of seven randomly selected days from the month and find the
average number per day
Count the number of vehicles traveling through the intersection each day for a month, and find the average number per day.
The type of sampling used in the first scenario is convenience sampling, as only customers who chose to participate in the online survey are included in the results.
For the second scenario, using the z-score formula z = (x - μ) / σ, where x = 47, μ = 50, and σ = 3:
z = (47 - 50) / 3
z = -1
Looking up the z-score of -1 in a standard normal distribution table, we find that the probability of a bag having fewer than 47 candies is approximately 0.1587.
Therefore, if 4 bags out of the sample have fewer than 47 candies, the probability of this happening is 0.1587^4, which is approximated to be 0.000866. This probability suggests that it is unlikely for only 4 bags out of the sample to have fewer than 47 candies.
For the last scenario, counting the number of vehicles traveling through the intersection on each of seven randomly selected days from the month and finding the average number per day will most likely provide a biased estimate of the daily number of vehicles, as randomly selecting the days may not represent the typical traffic patterns at the intersection.