Fuel Consumption Study Narrative
A study was conducted to compare fuel consumption of medium-size trucks for three brands of gasoline, A, B, and C. Four trucks of the same make and model were used in the experiment, and each gasoline brand was tested in each truck. Using each brand in the same truck has the effect of eliminating (blocking out) truck-to-truck variability. The data (litres per 100 km) are as follow:
Automobile
-Refer to Fuel Consumption Study Narrative. Suppose that prior to looking at the data, you had decided to compare the mean fuel consumption for gasoline brands A and B. Find a 90% confidence interval for this difference.

Question

Fuel Consumption Study Narrative
A study was conducted to compare fuel consumption of medium-size trucks for three brands of gasoline, A, B, and C. Four trucks of the same make and model were used in the experiment, and each gasoline brand was tested in each truck. Using each brand in the same truck has the effect of eliminating (blocking out) truck-to-truck variability. The data (litres per 100 km) are as follow:
Automobile 
-Refer to Fuel Consumption Study Narrative. Suppose that prior to looking at the data, you had decided to compare the mean fuel consumption for gasoline brands A and B. Find a 90% confidence interval for this difference.

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The Answer of Fuel Consumption Study Narrative
A study was conducted to compare fuel consumption of medium-size trucks for three brands of gasoline, A, B, and C. Four trucks of the same make and model were used in the experiment, and each gasoline brand was tested in each truck. Using each brand in the same truck has the effect of eliminating (blocking out) truck-to-truck variability. The data (litres per 100 km) are as follow:
Automobile 
-Refer to Fuel Consumption Study Narrative. Suppose that prior to looking at the data, you had decided to compare the mean fuel consumption for gasoline brands A and B. Find a 90% confidence interval for this difference.