| 
 
 
 
Question 1186540:  The economic dynamism, which is the index of productive growth in dollars for countries that are designated by the World Bank as middle-income are in table #8.3.9 ("SOCR data 2008," 2013).  Compute a 95% confidence interval for the mean economic dynamism of middle-income countries.
 
Table #8.3.9: Economic Dynamism ($) of Middle Income Countries 
25.8057	37.4511	51.915	43.6952	47.8506	43.7178	58.0767 
41.1648	38.0793	37.7251	39.6553	42.0265	48.6159	43.8555 
49.1361	61.9281	41.9543	44.9346	46.0521	48.3652	43.6252 
50.9866	59.1724	39.6282	33.6074	21.6643		
 
 
 Answer by CPhill(1987)      (Show Source): 
You can  put this solution on YOUR website! Here's how to calculate a 95% confidence interval for the mean economic dynamism of middle-income countries based on the provided data:
 
**1. Calculate the Sample Mean (x̄):**
 
Sum all the economic dynamism values and divide by the number of values (n = 25).
 
x̄ = (25.8057 + 37.4511 + ... + 21.6643) / 25 
x̄ ≈ 43.8727
 
**2. Calculate the Sample Standard Deviation (s):**
 
This measures the spread of the data.  You can use a calculator or statistical software to find this.
 
s ≈ 9.5626
 
**3. Find the Critical t-value:**
 
Since the sample size is small (n < 30), we use the t-distribution.  For a 95% confidence level and 24 degrees of freedom (n - 1 = 25 - 1 = 24), the critical t-value is approximately 2.064. You can find this using a t-table or a statistical calculator.
 
**4. Calculate the Margin of Error (ME):**
 
ME = t * (s / √n) 
ME = 2.064 * (9.5626 / √25) 
ME ≈ 3.9934
 
**5. Calculate the Confidence Interval:**
 
*   Lower Bound = x̄ - ME = 43.8727 - 3.9934 ≈ 39.8793 
*   Upper Bound = x̄ + ME = 43.8727 + 3.9934 ≈ 47.8661
 
**Result:**
 
The 95% confidence interval for the mean economic dynamism of middle-income countries is approximately (39.8793, 47.8661).
 
**Interpretation:**
 
We are 95% confident that the true mean economic dynamism for all middle-income countries lies within this interval. This means that if we were to repeat this study many times, 95% of the calculated confidence intervals would contain the true population mean. 
 
  | 
 
  
 
 |   
 
 |   
 |  |