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Stock-Based Compensation (Tables)
 3 Months Ended
Mar. 31, 2019
Schedule of Estimated Fair Value of TSR Performance-Based Restricted Stock Unit Awards Assumptions The fair value was estimated using the Monte Carlo simulation model with the following assumptions:
 
 
 
For the Three Months

Ended
 
 
 
March 31,
 
 
April 1,
 
 
 
2019
 
 
2018
 
Risk-free interest rate
 
 
2.6
%
 
 
2.2
%
Teradyne volatility-historical
 
 
31.8
%
 
 
26.8
%
NYSE Composite Index volatility-historical
 
 
12.0
%
 
 
12.4
%
Dividend yield
 
 
1.0
%
 
 
0.8
%
Fair Value of Stock Options Using Assumptions
The fair value of stock options was estimated using the Black-Scholes option-pricing model with the following assumptions:
 
 
 
For the Three Months

Ended
 
 
 
March 31,
 
 
April 1,
 
 
 
2019
 
 
2018
 
Expected life (years)
 
 
5.0
 
 
 
5.0
 
Risk-free interest rate
 
 
2.6
%
 
 
2.4
%
Volatility-historical
 
 
30.1
%
 
 
26.4
%
Dividend yield
 
 
1.0
%
 
 
0.8
%