1.6. From previous studies it was found that the average height of a plant is about 85 mm with a variance of 5. The area on which these studies were conducted ranged from between 300 and 500 square meters. An a An area of about 1 hectare was identified to study. They assumed that a population of 1200 plants exists in this lhectare area and want to study the height of the plants in this chosen area. They also assumed that the average height in millimetre (mm) and variance of the plants are similar to that of these previous studies. 1.6.1. A sample of 100 plants was taken and it was determined that the sample variance is 4. Find the standard error of the sample mean but also estimate the variance of the sample mean 1.6.2. In the previous study it was found that about 40% of the plants never have flowers. Assume the same proportion in the one-hectare population. In the sample of 100 plants the researchers found 55 flowering plants. Find the estimated standard error of p.

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1.6. From previous studies it was found that the average height of a plant is about 85 mm with a variance
of 5. The area on which these studies were conducted ranged from between 300 and 500 square
meters. An area of about 1 hectare was identified to study. They assumed that a population of 1200
plants exists in this lhectare area and want to study the height of the plants in this chosen area.
They also assumed that the average height in millimetre (mm) and variance of the plants are similar
to that of these previous studies.
1.6.1. A sample of 100 plants was taken and it was determined that the sample variance is 4. Find
the standard error of the sample mean but also estimate the variance of the sample mean
1.6.2. In the previous study it was found that about 40% of the plants never have flowers.
Assume the same proportion in the one-hectare population. In the sample of 100 plants the
researchers found 55 flowering plants. Find the estimated standard error of p.
1.7. Refer to information in 1.6 The one-hectare plot has different types of vegetation - shady areas,
sunny areas. The researchers want to establish whether the type of vegetation has an influence on
the mean height of the flower. They noticed that the two areas are more or less the same size and
the plants were spread evenly over the two areas. Recall the assumption of 1200 plants on this
1hectare plot. The researchers decide to investigate the shady and the sunny areas in order to
evaluate the mean heights as well record the number of flowering and non-flowering plants. A
sample of 20 plants was taken from the sunny area and a sample of 25 from the shady area. The
mean heights were 85 mm and 75 mm respectively and variances, 4 and 6 respectively. The
3
following steps were undertaken. Show how it applies to this case.
•
Establish that the plot needs to be divided according to vegetation -strata
•
Identify the different strata i = 1,2,...,!
N₁
Find the weight of each stratum W₂ =
N
•
Take a sample from each stratum 7₁, n2,..., n
Find the sample mean of each stratum X₁
ni
2i=1 Xll
.
Find the variance of each stratum
s} = 12"t(X - Xy)2
n-1
Estimate the stratified mean Xs = 1 W₁ X₁ as estimation of the population mean μ.
Estimate the standard error of the stratified mean.
●
•
Transcribed Image Text:1.6. From previous studies it was found that the average height of a plant is about 85 mm with a variance of 5. The area on which these studies were conducted ranged from between 300 and 500 square meters. An area of about 1 hectare was identified to study. They assumed that a population of 1200 plants exists in this lhectare area and want to study the height of the plants in this chosen area. They also assumed that the average height in millimetre (mm) and variance of the plants are similar to that of these previous studies. 1.6.1. A sample of 100 plants was taken and it was determined that the sample variance is 4. Find the standard error of the sample mean but also estimate the variance of the sample mean 1.6.2. In the previous study it was found that about 40% of the plants never have flowers. Assume the same proportion in the one-hectare population. In the sample of 100 plants the researchers found 55 flowering plants. Find the estimated standard error of p. 1.7. Refer to information in 1.6 The one-hectare plot has different types of vegetation - shady areas, sunny areas. The researchers want to establish whether the type of vegetation has an influence on the mean height of the flower. They noticed that the two areas are more or less the same size and the plants were spread evenly over the two areas. Recall the assumption of 1200 plants on this 1hectare plot. The researchers decide to investigate the shady and the sunny areas in order to evaluate the mean heights as well record the number of flowering and non-flowering plants. A sample of 20 plants was taken from the sunny area and a sample of 25 from the shady area. The mean heights were 85 mm and 75 mm respectively and variances, 4 and 6 respectively. The 3 following steps were undertaken. Show how it applies to this case. • Establish that the plot needs to be divided according to vegetation -strata • Identify the different strata i = 1,2,...,! N₁ Find the weight of each stratum W₂ = N • Take a sample from each stratum 7₁, n2,..., n Find the sample mean of each stratum X₁ ni 2i=1 Xll . Find the variance of each stratum s} = 12"t(X - Xy)2 n-1 Estimate the stratified mean Xs = 1 W₁ X₁ as estimation of the population mean μ. Estimate the standard error of the stratified mean. ● •
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