A soil scientist has just developed a new type of fertilizer and she wants to determine whether it helps carrots grow larger. She sets up several pots of soil and plants one carrot seed in each pot. Fertilizer is added to half the pots. All the pots are placed in a temperature-controlled greenhouse where they receive adequate light and equal amounts of water. After two months of growth, the scientist harvests the carrots and weighs them (in kilograms). Below is a data table showing the weight of the carrots at the end of the growing period from the two treatment groups. Here is a hyperlink to the data.
Sample ID | Control | Nitrogen Treatment |
1 | 0.331 | 0.419 |
2 | 0.375 | 0.727 |
3 | 0.385 | 0.766 |
4 | 0.474 | 0.741 |
5 | 0.223 | 0.182 |
6 | 0.261 | 0.821 |
7 | 0.4 | 0.251 |
8 | 0.349 | 0.778 |
9 | 0.203 | 0.641 |
10 | 0.332 | 0.368 |
11 | 0.231 | 0.732 |
12 | 0.457 | 0.453 |
13 | 0.216 | 0.45 |
14 | 0.29 | 0.196 |
15 | 0.218 | 0.325 |
16 | 0.353 | 0.706 |
17 | 0.285 | 0.5 |
18 | 0.463 | 0.691 |
19 | 0.371 | 0.691 |
20 | 0.411 | 0.755 |
21 | 0.407 | 0.35 |
22 | 0.249 | 0.395 |
23 | 0.298 | 0.519 |
24 | 0.4 | 0.285 |
25 | 0.361 | 0.423 |
26 | 0.488 | 0.363 |
27 | 0.338 | 0.737 |
28 | 0.215 | 0.538 |
29 | 0.486 | 0.626 |
30 | 0.235 | 0.329 |
When analyzing this dataset with a t-test, the hypothesis states that the average size of the carrots from each treatment are the same, whereas the hypothesis states that the fertilized carrots are larger in size.
To analyze this data set, the scientist should use a -tailed t-test.
After performing a t-test assuming equal variances using the data analysis add-in for MS Excel, what is the calculated t-value for this data set?
Report the appropriate critical t value, based on your decision of a one- or two-tailed test, calculated by MS Excel using the Data Analysis add-in.
What is the appropriate p value for the t-test?
Would you reject or fail to reject the null hypothesis?
Answer:
When analyzing this dataset with a t-test, the null hypothesis states that the average size of the carrots from each treatment are the same, whereas the alternate hypothesis states that the fertilized carrots are larger in size.
To analyze this data set, the scientist should use a one -tailed t-test.
Let treatment group=1 and control group as 2.
After performing a t-test assuming equal variances using the data analysis add-in for MS Excel, what is the calculated t-value for this data set?
t-Test: Two-Sample Assuming Equal Variances |
||
Nitrogen Treatment |
Control |
|
Mean |
0.525266667 |
0.336833333 |
Variance |
0.038553995 |
0.008087385 |
Observations |
30 |
30 |
Pooled Variance |
0.02332069 |
|
Hypothesized Mean Difference |
0 |
|
df |
58 |
|
t Stat |
4.778951908 |
|
P(T<=t) one-tail |
6.21585E-06 |
|
t Critical one-tail |
1.671552762 |
|
P(T<=t) two-tail |
1.24317E-05 |
|
t Critical two-tail |
2.001717484 |
calculated t-value = 4.7790
Report the appropriate critical t value, based on your decision of a one- or two-tailed test, calculated by MS Excel using the Data Analysis add-in.
critical t value =1.6716
What is the appropriate p value for the t-test?
appropriate p value=6.2159E-06
Would you reject or fail to reject the null hypothesis?
We reject the null hypothesis
A soil scientist has just developed a new type of fertilizer and she wants to determine whether i...
A soil scientist has just developed a new type of fertilizer and she wants to determine whether it helps carrots grow larger. She sets up several pots of soil and plants one carrot seed in each pot. Fertilizer is added to half the pots. All the pots are placed in a temperature-controlled greenhouse where they receive adequate light and equal amounts of water. After two months of growth, the scientist harvests the carrots and weighs them (in kilograms). Below is...
Sample ID Control Fertilizer Treatment 1 0.358 0.336 2 0.338 0.438 3 0.488 0.458 4 0.374 0.797 5 0.411 0.588 6 0.442 0.326 7 0.376 0.193 8 0.334 0.297 9 0.498 0.486 10 0.403 0.203 11 0.473 0.5 12 0.238 0.214 13 0.298 0.599 14 0.222 0.2 15 0.318 0.598 16 0.337 0.454 17 0.398 0.563 18 0.35 0.692 19 0.285 0.685 20 0.383 0.493 21 0.275 0.361 22 0.332 0.206 23 0.469 0.701 24 0.497 0.255 25 0.352 0.541...
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