Confidence Interval on Difference between Means, Independent Groups, Standard Deviation Known (3 of 3)

---

Next section: Difference between independent groups, σ estimated

The 95% confidence interval is: -127 ± (1.96)(52.836) = -127 ± 103.559

-230.56 ≤ μ₁- μ₂ ≤ -23.44

here μ₁is the mean for simple RT and μ₂ is the mean for choice RT.


Summary of Computations

1. Compute M_d = M₁ - M₂
   
   
2. Compute
   
   
3. Find z (1.96 for 95% interval; 2.58 for 99% interval)
   
   
4. Lower limit = M_d - z
   
   
5. Upper limit = M_d + z
   
   
6. Lower limit   ≤ μ₁ - μ₂ ≤  Upper limit

Assumptions:

1. The populations are each normally distributed.
   
   
2. σ is known
   
   
3. Scores are sampled randomly and are independent

Next section: Difference between independent groups, σ estimated